Apparently the "rule" is that he didn't give himself up because he didn't slide feet first.
I don't know how it's written, but to me a slide is a slide and I guarantee you if someone had buried him, it would've been a 15.
Definitely not the stupidest call by an official tonight though, which belonged to the guy who flagged Washington for belting Stamps in the end zone. Flag the play, not the result. Thought Odell Willis got tagged for one lame one too on Drew Willy. You can't hit a guy low, that doesn't mean you can't pull him down by his leg.