Create mobile account for two different users with the same name fails

We discovered this today, and we haven't found any information about it anywhere, so...

If you have a mac bound to an Active Directory where there are users with the same name but different usernames, you may see that certain users cannot login to the mac. This happens when you have "Create mobile account at login" activated and a user tries to login who has the same name as a previously logged in user.

What is going wrong then? I don't know exactly, besides that it's the "RecordName" key that is the problem. There cannot be two users in the local database that has a value in RecordName matching any other user's value in RecordName.

If you change the value to something else on the first user, the second user can login.

Delete the value:
sudo dscl . delete /Users/uname1 RecordName "John Doe"

Append a new value:
sudo dscl . append /Users/uname1 RecordName "John Marc Doe"

Or simply change:
sudo dscl . change /Users/uname1 RecordName "John Doe" "John Marc Doe"

UPDATE 2010-10-20
I made a bugreport to Apple regarding this yesterday and got a response that they need logs. I will upload the logs today to Apple and then we'll see what they have to say about it...

UPDATE 2010-10-25
Apple says this is expected behavior. I have replied that I disagree.