Of, course, he didn't say that. He also didn't mention that DOMA passed both houses of Congress by wide margins. Further, less than two years ago President Obama's official position was in opposition of gay marriage. It's one thing to have your position "evolve" as the president claimed his did on this issue. It's another to have been holding a position just for political expediency when you didn't really believe in the first place.
I don't believe the president when he says his position evolved on this issue. I don't have to believe Clinton. He's not even bothering to say that.