User blog comment:Saratje/PC release date explained - Skyrim: Dragonborn DLC/@comment-3492791-20121128054340/@comment-3492791-20121129001019

Patches are subject to technical issues, not exclusivity. Different platforms may receive patches at different times, because each platform requires a different method to solving similar problems. Thus, some consoles may have their patches actually finished first before all others. Since the game was lead on 360, it is likely the easiest for them to program on.

Also, PC recieve the 1.8 patch first as a beta.