Sorry I don't think my example was good enough.
It was logging when using include_vars. I will create an example playbook and raise a defect on github
TASK: [user-builder | include_vars vault/keys.yml] ****************************
ok: [localhost] => {"ansible_facts": {"vault_builder_id_rsa": "-----BEGIN RSA PRIVATE KEY-----
.......\7f0iXxEglf8a3wGD3qEVCNLNDxzVJ6grnFsDa0IfBey\n3VG7Sawu3vkpf0jnd21knv90YspfEx3zjGHpM2inT4AfVM8vjMAxgF9w3jZIj2w2\n2D47yPaF2xv8PvasNCEHcs7vCKd2AqtU5ySqb9ajJzvZE7jwqQE=\n-----END RSA PRIVATE KEY-----\n"}}
TASK: [user-builder | include_vars vault/cvs.yml] *****************************
ok: [localhost] => {"ansible_facts": {"vault_builder_cvspass": "/1 .......n"}}
TASK: [user-builder | include_vars vault/subversion.yml] **********************
ok: [localhost] => {"ansible_facts": {"vault_builder_subversion_cert_data": "K 10\nascii_cert\nV 948\nMIICwzCCAiwCCQC7AE/MsC2l8jANBgkqhkiG9w0BAQUFADCDVQQHEwZEdWJsaW4xFzAVBgNVBAoTDlBhZGR5IFBvd2VyIElUMQwwCgYDVQQLEwNTQ00xKDAmBgNVBAMTH2R1YmRjqT6r0Dta59bA9kiVqzI\nK 8\nfailures\nV 2\n12\nK 15\nsvn:realmstring\nV 27\nhttps://
217.112.150.122:443\nEND\n", "vault_builder_subversion_serverrecord": "29c985a08edc7fae1dde0fe590b47938"}}
J