For me, the back down is a charge. I assume that's what we are referring to here, not some special rule. But the only way it ever gets called is with the defender exaggerating the hit. I wouldn't call that a flop, because it really is a charge. But the defender shouldn't have to go flying across the floor for a foul to be called. It just leads to more fake flops. It's a bit like soccer. Guys dive (partially) because they often won't get a call if they don't go down.
Villanova guys just slam into the defender over and over until they get within a few feet of the rim where they can make a shot or get fouled. It's often worse with bigger guards than centers. I think Caleb Daniels is great. Total warrior. But he shouldn't be allowed to just literally push his way into the restricted area.
Sanogo does the back down sometimes, but it's not really his game with his footwork. I think he'd be fine with that called a bit closer.
It does seem like Hurley's D is a bit susceptible to the back down. He doesn't seem to like to double, even when someone is taking advantage of a mismatch. Seton Hall did it with Richmond last year, Villanova did it, and I think a couple teams have done it against Karaban when he's undersized. So, while I think it should be a foul, I also think we should do a better job defending it. But
@Palatine may be right about the reason, and that may be a good decision in the end.