I get the field you're looking for if I specify a date.
$ gam version
Python 2.7.12 64-bit final
google-api-python-client 1.6.2
oauth2client 4.1.2
Darwin-14.5.0-x86_64-i386-64bit x86_64
Path: /Users/Ross/Documents/GoogleApps/GAM
Got 1 users
email,date,classroom:num_courses_created,classroom:num_posts_created,classroom:role,classroom:last_interaction_time,accounts:admin_set_name,accounts:is_disabled,accounts:disabled_reason,accounts:drive_used_quota_in_mb,accounts:first_name,accounts:gmail_used_quota_in_mb,accounts:gplus_photos_used_quota_in_mb,accounts:is_2sv_enforced,accounts:is_2sv_enrolled,accounts:is_delegated_admin,accounts:is_less_secure_apps_access_allowed,accounts:is_super_admin,accounts:is_suspended,accounts:last_name,accounts:num_authorized_apps,accounts:num_roles_assigned,accounts:num_security_keys,accounts:creation_time,accounts:last_login_time,accounts:last_sso_time,accounts:total_quota_in_mb,accounts:used_quota_in_mb,accounts:used_quota_in_percentage,accounts:user_has_overridden_name,gplus:num_plusones,gplus:num_plusones_received,gplus:num_replies,gplus:num_replies_received,gplus:num_reshares,gplus:num_reshares_received,gplus:num_shares,docs:num_owned_google_documents_created,docs:num_owned_google_documents_edited,docs:num_owned_google_documents_trashed,docs:num_owned_google_documents_viewed,docs:num_owned_google_drawings_created,docs:num_owned_google_drawings_edited,docs:num_owned_google_drawings_trashed,docs:num_owned_google_drawings_viewed,docs:num_owned_google_forms_created,docs:num_owned_google_forms_edited,docs:num_owned_google_forms_trashed,docs:num_owned_google_forms_viewed,docs:num_owned_google_presentations_created,docs:num_owned_google_presentations_edited,docs:num_owned_google_presentations_trashed,docs:num_owned_google_presentations_viewed,docs:num_owned_google_spreadsheets_created,docs:num_owned_google_spreadsheets_edited,docs:num_owned_google_spreadsheets_trashed,docs:num_owned_google_spreadsheets_viewed,docs:num_owned_items_created,docs:num_owned_items_edited,docs:num_owned_items_trashed,docs:num_owned_items_viewed,docs:num_owned_other_types_created,docs:num_owned_other_types_edited,docs:num_owned_other_types_trashed,docs:num_owned_other_types_viewed,gmail:is_gmail_enabled,gmail:num_emails_exchanged,gmail:num_emails_received,gmail:num_emails_sent,gmail:num_spam_emails_received,gmail:last_access_time,gmail:last_imap_time,gmail:last_interaction_time,gmail:last_pop_time,gmail:last_webmail_time,drive:num_google_documents_created,drive:num_google_documents_edited,drive:num_google_documents_trashed,drive:num_google_documents_viewed,drive:num_google_drawings_created,drive:num_google_drawings_edited,drive:num_google_drawings_trashed,drive:num_google_drawings_viewed,drive:num_google_forms_created,drive:num_google_forms_edited,drive:num_google_forms_trashed,drive:num_google_forms_viewed,drive:num_google_presentations_created,drive:num_google_presentations_edited,drive:num_google_presentations_trashed,drive:num_google_presentations_viewed,drive:num_google_spreadsheets_created,drive:num_google_spreadsheets_edited,drive:num_google_spreadsheets_trashed,drive:num_google_spreadsheets_viewed,drive:num_items_created,drive:num_items_edited,drive:num_items_trashed,drive:num_items_viewed,drive:num_other_types_created,drive:num_other_types_edited,drive:num_other_types_trashed,drive:num_other_types_viewed,drive:num_owned_external_items_added,drive:num_owned_google_documents_added,drive:num_owned_google_documents_created,drive:num_owned_google_documents_delta,drive:num_owned_google_documents_edited,drive:num_owned_google_documents_removed,drive:num_owned_google_documents_trashed,drive:num_owned_google_documents_viewed,drive:num_owned_google_drawings_added,drive:num_owned_google_drawings_created,drive:num_owned_google_drawings_delta,drive:num_owned_google_drawings_edited,drive:num_owned_google_drawings_removed,drive:num_owned_google_drawings_trashed,drive:num_owned_google_drawings_viewed,drive:num_owned_google_forms_added,drive:num_owned_google_forms_created,drive:num_owned_google_forms_delta,drive:num_owned_google_forms_edited,drive:num_owned_google_forms_removed,drive:num_owned_google_forms_trashed,drive:num_owned_google_forms_viewed,drive:num_owned_google_presentations_added,drive:num_owned_google_presentations_created,drive:num_owned_google_presentations_delta,drive:num_owned_google_presentations_edited,drive:num_owned_google_presentations_removed,drive:num_owned_google_presentations_trashed,drive:num_owned_google_presentations_viewed,drive:num_owned_google_spreadsheets_added,drive:num_owned_google_spreadsheets_created,drive:num_owned_google_spreadsheets_delta,drive:num_owned_google_spreadsheets_edited,drive:num_owned_google_spreadsheets_removed,drive:num_owned_google_spreadsheets_trashed,drive:num_owned_google_spreadsheets_viewed,drive:num_owned_internal_items_added,drive:num_owned_items_added,drive:num_owned_items_created,drive:num_owned_items_delta,drive:num_owned_items_edited,drive:num_owned_items_removed,drive:num_owned_items_trashed,drive:num_owned_items_viewed,drive:num_owned_items_with_visibility_anyone_in_domain_added,drive:num_owned_items_with_visibility_anyone_in_domain_delta,drive:num_owned_items_with_visibility_anyone_in_domain_removed,drive:num_owned_items_with_visibility_anyone_in_domain_with_link_added,drive:num_owned_items_with_visibility_anyone_in_domain_with_link_delta,drive:num_owned_items_with_visibility_anyone_in_domain_with_link_removed,drive:num_owned_items_with_visibility_anyone_with_link_added,drive:num_owned_items_with_visibility_anyone_with_link_delta,drive:num_owned_items_with_visibility_anyone_with_link_removed,drive:num_owned_items_with_visibility_private_added,drive:num_owned_items_with_visibility_private_delta,drive:num_owned_items_with_visibility_private_removed,drive:num_owned_items_with_visibility_public_added,drive:num_owned_items_with_visibility_public_delta,drive:num_owned_items_with_visibility_public_removed,drive:num_owned_items_with_visibility_shared_externally_added,drive:num_owned_items_with_visibility_shared_externally_delta,drive:num_owned_items_with_visibility_shared_externally_removed,drive:num_owned_items_with_visibility_shared_internally_added,drive:num_owned_items_with_visibility_shared_internally_delta,drive:num_owned_items_with_visibility_shared_internally_removed,drive:num_owned_other_types_added,drive:num_owned_other_types_created,drive:num_owned_other_types_delta,drive:num_owned_other_types_edited,drive:num_owned_other_types_removed,drive:num_owned_other_types_trashed,drive:num_owned_other_types_viewed
test...@rdschool.org,2017-09-01,0,0,teacher,1970-01-01T00:00:00.000Z,Test User1,False,,0,Test,0,0,False,False,True,False,False,False,User1,2,1,0,2015-06-29T19:52:28.000Z,2017-09-01T12:19:07.000Z,1970-01-01T00:00:00.000Z,-1,0,0,False,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,True,1,1,0,0,2017-09-02T02:30:18.000Z,1970-01-01T00:00:00.000Z,2017-08-31T14:38:35.000Z,1970-01-01T00:00:00.000Z,2017-08-31T16:00:40.000Z,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
I do not get the field you're looking for if I don't specify a date.
Got 1 users
email,date,accounts:admin_set_name,accounts:is_disabled,accounts:disabled_reason,accounts:first_name,accounts:is_2sv_enforced,accounts:is_2sv_enrolled,accounts:is_delegated_admin,accounts:is_less_secure_apps_access_allowed,accounts:is_super_admin,accounts:is_suspended,accounts:last_name,accounts:num_authorized_apps,accounts:num_roles_assigned,accounts:num_security_keys,accounts:creation_time,accounts:last_login_time,accounts:last_sso_time,accounts:user_has_overridden_name,docs:num_owned_google_documents_created,docs:num_owned_google_documents_edited,docs:num_owned_google_documents_trashed,docs:num_owned_google_documents_viewed,docs:num_owned_google_drawings_created,docs:num_owned_google_drawings_edited,docs:num_owned_google_drawings_trashed,docs:num_owned_google_drawings_viewed,docs:num_owned_google_forms_created,docs:num_owned_google_forms_edited,docs:num_owned_google_forms_trashed,docs:num_owned_google_forms_viewed,docs:num_owned_google_presentations_created,docs:num_owned_google_presentations_edited,docs:num_owned_google_presentations_trashed,docs:num_owned_google_presentations_viewed,docs:num_owned_google_spreadsheets_created,docs:num_owned_google_spreadsheets_edited,docs:num_owned_google_spreadsheets_trashed,docs:num_owned_google_spreadsheets_viewed,docs:num_owned_items_created,docs:num_owned_items_edited,docs:num_owned_items_trashed,docs:num_owned_items_viewed,docs:num_owned_other_types_created,docs:num_owned_other_types_edited,docs:num_owned_other_types_trashed,docs:num_owned_other_types_viewed,gmail:is_gmail_enabled,gmail:num_emails_exchanged,gmail:num_emails_received,gmail:num_emails_sent,gmail:num_spam_emails_received,gmail:last_access_time,gmail:last_imap_time,gmail:last_interaction_time,gmail:last_pop_time,gmail:last_webmail_time,drive:num_google_documents_created,drive:num_google_documents_edited,drive:num_google_documents_trashed,drive:num_google_documents_viewed,drive:num_google_drawings_created,drive:num_google_drawings_edited,drive:num_google_drawings_trashed,drive:num_google_drawings_viewed,drive:num_google_forms_created,drive:num_google_forms_edited,drive:num_google_forms_trashed,drive:num_google_forms_viewed,drive:num_google_presentations_created,drive:num_google_presentations_edited,drive:num_google_presentations_trashed,drive:num_google_presentations_viewed,drive:num_google_spreadsheets_created,drive:num_google_spreadsheets_edited,drive:num_google_spreadsheets_trashed,drive:num_google_spreadsheets_viewed,drive:num_items_created,drive:num_items_edited,drive:num_items_trashed,drive:num_items_viewed,drive:num_other_types_created,drive:num_other_types_edited,drive:num_other_types_trashed,drive:num_other_types_viewed,drive:num_owned_external_items_added,drive:num_owned_google_documents_added,drive:num_owned_google_documents_created,drive:num_owned_google_documents_delta,drive:num_owned_google_documents_edited,drive:num_owned_google_documents_removed,drive:num_owned_google_documents_trashed,drive:num_owned_google_documents_viewed,drive:num_owned_google_drawings_added,drive:num_owned_google_drawings_created,drive:num_owned_google_drawings_delta,drive:num_owned_google_drawings_edited,drive:num_owned_google_drawings_removed,drive:num_owned_google_drawings_trashed,drive:num_owned_google_drawings_viewed,drive:num_owned_google_forms_added,drive:num_owned_google_forms_created,drive:num_owned_google_forms_delta,drive:num_owned_google_forms_edited,drive:num_owned_google_forms_removed,drive:num_owned_google_forms_trashed,drive:num_owned_google_forms_viewed,drive:num_owned_google_presentations_added,drive:num_owned_google_presentations_created,drive:num_owned_google_presentations_delta,drive:num_owned_google_presentations_edited,drive:num_owned_google_presentations_removed,drive:num_owned_google_presentations_trashed,drive:num_owned_google_presentations_viewed,drive:num_owned_google_spreadsheets_added,drive:num_owned_google_spreadsheets_created,drive:num_owned_google_spreadsheets_delta,drive:num_owned_google_spreadsheets_edited,drive:num_owned_google_spreadsheets_removed,drive:num_owned_google_spreadsheets_trashed,drive:num_owned_google_spreadsheets_viewed,drive:num_owned_internal_items_added,drive:num_owned_items_added,drive:num_owned_items_created,drive:num_owned_items_delta,drive:num_owned_items_edited,drive:num_owned_items_removed,drive:num_owned_items_trashed,drive:num_owned_items_viewed,drive:num_owned_items_with_visibility_anyone_in_domain_added,drive:num_owned_items_with_visibility_anyone_in_domain_delta,drive:num_owned_items_with_visibility_anyone_in_domain_removed,drive:num_owned_items_with_visibility_anyone_in_domain_with_link_added,drive:num_owned_items_with_visibility_anyone_in_domain_with_link_delta,drive:num_owned_items_with_visibility_anyone_in_domain_with_link_removed,drive:num_owned_items_with_visibility_anyone_with_link_added,drive:num_owned_items_with_visibility_anyone_with_link_delta,drive:num_owned_items_with_visibility_anyone_with_link_removed,drive:num_owned_items_with_visibility_private_added,drive:num_owned_items_with_visibility_private_delta,drive:num_owned_items_with_visibility_private_removed,drive:num_owned_items_with_visibility_public_added,drive:num_owned_items_with_visibility_public_delta,drive:num_owned_items_with_visibility_public_removed,drive:num_owned_items_with_visibility_shared_externally_added,drive:num_owned_items_with_visibility_shared_externally_delta,drive:num_owned_items_with_visibility_shared_externally_removed,drive:num_owned_items_with_visibility_shared_internally_added,drive:num_owned_items_with_visibility_shared_internally_delta,drive:num_owned_items_with_visibility_shared_internally_removed,drive:num_owned_other_types_added,drive:num_owned_other_types_created,drive:num_owned_other_types_delta,drive:num_owned_other_types_edited,drive:num_owned_other_types_removed,drive:num_owned_other_types_trashed,drive:num_owned_other_types_viewed
test...@rdschool.org,2017-09-05,Test User1,False,,Test,False,False,True,False,False,False,User1,2,1,0,2015-06-29T19:52:28.000Z,2017-09-03T15:38:16.000Z,1970-01-01T00:00:00.000Z,False,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,True,1,1,0,0,2017-09-06T02:30:18.000Z,1970-01-01T00:00:00.000Z,2017-08-31T14:38:35.000Z,1970-01-01T00:00:00.000Z,2017-08-31T16:00:40.000Z,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
Ross