Guest Directors for The Office... Why?

The last two weeks have featured Joss Whedon (of Buffy the Vampire Slayer fame) and J.J. Abrams (director of Alias and Lost) directing episodes of The Office. While I realize that a) every episode needs someone to direct it and b) a guest director might be a nice promotional thing, this seems to go against the very nature of The Office. It is supposed to be a documentary, and every clip we are shown is supposed to be captured by a real film crew working with the folks at Dunder Mifflin. SO, if we buy into this premise, every episode should LOOK exactly the same (as far as camera angles and the production goes). So, bringing in someone to guest direct just seems kind of silly. Now, having someone come in to write an episode would be interesting, but even then there are so many story arcs to consider there's little leeway in doing anything major (you can't have Dwight get his hand chopped off or anything like that).

Personally, I think guest directors can have the best impact on procedurals (i.e. Law and Order, CSI) where they can shake up the presentation of what is a pretty stale formula at times (Law and Order: CI seems to have been doing this lately and it has definitely enhanced the quality of the show).