PUP-4617 added the ability to print custom OIDs to the puppet cert print CLI. Later it was removed and replaced with puppet ssl show, but the new command doesn't support the custom OID functionality. See PUP-4617.
"puppet ssl show" now shows the human readable names for certificate extensions containing custom OIDs provided the `trusted_oid_mapping_file` exists. This functionality existed in "puppet cert print" but was lacking in the new command.