Password Change - Difference between OpenSSO and OAM

When migrating OpenSSO to OAM, I noticed there is a difference between OpenSSO and OAM on handing end user self password change scenario.

End user password change via OpenSSO:   self change. The directory server change log shows the password has been changed by the user self.

End user password change OAM: admin change. The directory server change log shows the password has been changed by the user configured as BIND DN in OAM identity store.