Can't update Boot Camp in Windows 7 (MacbookPro9,1)
So my first guess was right, the WindowsSupport.dmg downloaded from the post's links installed Boot Camp 4.0.0.1. I just checked the details tab on the Bootcamp executable (Program Files\Boot Camp), didn't think of that before.

Nonetheless, I still believe the updates should be prepared to check for more recent versions and throw a different message.