Calling the flop

[lmeadski]

This is part of conversation from a previous thread and I'd like you guys' opinion: A1 has the ball and makes play to the hole. He leaves his feet to shoot (actually, he doesn't have to leave his feet...it's your choice). Before contact is made, B1 begins to flop. Contact is made, A1 splits B1 right down the breast bone. Both players end up on the floor. Shouldn't this be an automatic blocking foul? Didn't B1 lose his "legal guarding position" status when he began his flop? Other posters mentioned that they don't call a charge or a block on this, due to the flop.