vCloud Director conflicts local user with an import SAML User if use same login id and it throw an authentication failed when use same login Id

if create local user name in vCD Org which exist in SAML user (exist same login in AD/SSO Identity management system) , then vCD SSO login throw an authentication failed.

For example,

Create a “User1” in local vCD org, it work without SSO login.

Create “User1” login id in SSO Identity management system (a SAML user), tag to the group, and import group to vCD and enabled SSO federation.

In this time, vCD redirect to OpenAM login page and openAM authenticate successfully, but vCD throw an authentication failed because of local user1 conflict.

It work well, If remove the local “User1”.

Do vCD have custom exception on for duplicate User ID or conflict user scenario instead of authentication failed?