That's a cynical view to take, but not entirely implausible, of course. I've thought the same thing myself. However, the discussion in the comments section of the Gamasutra article is worth a read - Peter David, who wrote Shadow Complex's dialogue and is pro-gay rights, chips in with a few opinions of his own. It was getting quite heated yesterday, but it was certainly an interesting read.
Thing is, people were talking about Shadow Complex loads already. It was the "big one" out of the Summer of Arcade titles for many people. If it was a marketing ploy, it really wasn't necessary.
It is cynical but here's why I think this -
a) call it a hunch, but his kind of 2d game doesn't appear to be the type at all popular with <18 demo
b) the chair devs can't be counted on to provide any soundbites or anything that provides decent copy - they named their company after a friggin chair. A CHAIR. Then they go on to talks about the Platonic theory of forms on their website. I'm not kidding, read the "about us" section. Really, Plato. I want to hug the guy that's working PR on this project for having to deal with them. Chair's not exactly Peter "I'm a walking publicity machine" Molyneux.
c) due to the above extremely naive mentality and the fact MS is publishing, it would be relatively simple to pull a very ingenious campaign where you leak Card's involvement in NoM (which is only listed in a 4/23 press release, not on the NoM website proper, so I find it extremely odd anyone "found" it) like this without them knowing at all. The devs inevitable dissociation from C's beliefs would even sound believable and non-contrived because it would be real.
d) Popular xbox live title is good, but a game like this should have legs, and preferably sequels using the same game engine (students of Castlevania for GBA and DS will note that that can work out quite nicely). More is better. Current publicity nets you a popular game. More publicity nets you a popular series of games with minimal additional overhead.