Yep. there's a new AR in blue that speaks to that. 6-3-4-IV
If a B player is engaged in a block with an A player, and the ball hits the B player, this is not forced touching. the way i've heard it described is if two guys are "standing straight up blocking each other" and the ball happens to hit one of them, there is no forced touching, because the block(s) weren't responsible for the contact with the ball.
it really has to be one guy pushing another guy into the ball.