EP User Mapping From LDAP Active Directory Data Source

Experts,

We are trying to perform user mapping on SSO between LDAP User and SAP ECC User through the Enterprise Portal.

Acording to this guide:

https://help.sap.com/saphelp_nw73/helpdata/en/46/3e82c69e6802ece10000000a155369/frameset.htm

It Seems like the only way to achieve this is through UME users

in fact you can see from the screen.

UME user:

LDAP user:

Can anyone confirm this limit or provide a solution?

PS:

Active Directory LDAP attributes cannot be modified.

Thank you very much.