Since user must authenticate in pre-boot, fact that same user name is shown in Windows should not matter.
Actually you wanted to have SSO enabled, and it should go further, fill both fields of user credentials and login to Windows seemlesly. In your case that part did not work properly.
No, if a user authenticates in preboot, he / she gets logged into windows.
The problem is the user has logged off the computer again, then the username will be prefilled in the username textbox.
Also after I perform a machine recovery, when the Windows logon comes up, the last logged on username is already prefilled in.
This only occurs on Windows 7 machines, not XP.