If I remember right they flipped Mario after they'd set, and when the OLine slanted at him they slipped Kiko in the back door.
Newton never knew he was coming or he would have done exactly what you suggested. But with only sending one extra rusher the Bills didn't really compromise the integrity of their umbrella and even if Newton does get it out he's throwing it in the middle of the field where that play is just going to die a slow, ugly death.