But wasn't the OS still being worked on after E3? I remember seeing a video, not sure it it was on CNN or Gametrailers, that had an inside look at the Xbox One OS. In the video, the MS tech/programmer said they are still months away from finalizing the OS for the Xbox One.I don't think anyone knows for sure, but I would think the OS would have to be tested and QA-d by the time production started or even earlier.
Actually, thinking about it...This was before the Xbox 180 so the patching of the OS wouldn't have been a problem since the console was have required a always 24 hours internet checking.
Guess I answered my own question lol