I agree with Mike. It appears that B "orchestrated" a false start. As I was thinking about this situation, I was wondering how much intent has to do with penalizing abrupt defensive actions. If B anticipates the snap count and starts early but has not entered the neutral zone, and then A reacts prior to the snap, we would still have a false start wouldn't we? My question is, do we have to judge intent to penalize "abrupt defensive actions"?