Adding a UPN, when I log in using that UPN it doesn't use the same profile
Windows uses the user account SID to keep track and relate user profiles to Active Directory users. Changing the UPN or the SamAccountName does not change the SID of a user account. In fact, the SID is immutable.
If you only changed the UPN, this has no impact on the SID and consequently to the user profile that is loaded when you log on to a computer where you logged in before the change.
If you experience an issue with the user profile, the cause does not correlate to the change.