Can cross-IDCS user accounts be mapped when usernames in two IDCS do not match?

Summary:

Is there an ability to integrate two applications, such as Narrative Reporting (EPM SaaS) and Essbase (in OCI) to work together, although in one IDCS username is "abc123" (username=email is unchecked) and in the other it is adc_123@mycompany.com, while the email fields in both system match?

Content (please ensure you mask any confidential information):

Our Narrative Reporting EPM is in one IDCS domain and usernames are mapped to Employee IDs, while Essbase is in OCI in a different IDCS and uses employee emails as usernames. In both applications users login via SSO. So while executing reports using Native account worked fine, end users are getting "User **** is not authorized to access this connection". I know in OAC there are various ways to set user authentication when running reports. I wonder if Oracle can suggest a good solution how this account mismatch can be resolved. Is there a way to map two different usernames