I still don't see it. I've seen balls caught with 2 feet in, and then the player out of bounds, drops the ball, or it hits the ground, and it's ruled incomplete. In a running play, yes.. as soon as you leap ahead and the ball crosses the plane, it's over. But in a catch, you must finish the catch. It doesn't matter if it's in the endzone or not.
So.. I don't agree with it. Didn't matter in the end, but I still think that was not a touchdown.