The issue is just as much AW leaping towards the head of the TE on top of the perceived head contact. What TheCardFan is saying is, if AW had stayed on his feet and drilled Heap, no penalty would have ensued. The hit would have been almost as spectacular and the Ravens would not have gotten an extra 15 yards.
Refs are training in such a way that when a player leaves his feet and goes up towards the head, flags start to get reached for. Also remember that a ref doesn't have the advantage of seeing in in slo motion and all he gets is real time hit explosions. The problem is, it was close...I think it was a questionable call personally but if you take the call in it's proper context, the hit was not really clean. Bad call that hurt though