User blog comment:Saratje/PC release date explained - Skyrim: Dragonborn DLC/@comment-178.240.46.62-20121230231704/@comment-67.185.191.169-20121231005547

Windows may be owned my Microsloth, but the PC is not. They have zero control over what is or is not released for the PC, whereas they have almost complete control over what is released for the Xbox.

The games may be MADE on a PC, but the development environment is not the same, given the differences in hardware and soft/firmware. Just because it's built on a PC doesn't mean it will run on one, for several reasons.