Another great thing to look for is displacement and if the dribbler stops at contact. If the offensive player is able to stay under control and stop at contact it's probably a no-call. If the offensive player ends up on top of the defender on the floor then you have some obvious displacement and need a whistle.

I had a weird block/charge today where the dribbler faked right and went left. The defender maintained LGP and the contact happened with the dribbler 's right leg on the defenders left leg. The defender ended up shooting straight back and the offensive player kinda faded away to the left. To everyone in the world (and the coach who blew up) it looked like a block but all I saw was a legal defender and displacement. The contact doesn't have to occur right in the middle of the chest to have a charge, and this contact was nearly on the side of the body.

I, too, think you should have a call on train wrecks. In the OP the player hit the floor hard. Calling stuff like this may prevent future injuries or other nonsense. If you don't call the PC, the kid that was on the floor may think it is OK to try the same thing, or you get jawing, or other retaliation.

If the game video is sent to the State, assignor, whoever... What is easier to defend? Calling a foul that is a foul by rule? Or giving hollow platitudes?

If a defender flops, that defender almost always interferes with a play by going to the floor with some sort of contact (could even be minor). If they trip, cause any contact at all... Call a block on a flopping player and I guarantee they will only flop 5 times during the game.

Train Wrecks ...
 

I had such a wreck Friday night. I'm the new lead after a division line steal, couldn't really get ahead of the play, and decided to try to get a good angle instead. From the defender's movements, I could have sworn that she was going to try to block the shot, and readied myself for that possibility, but at the last split second she decided to try to take the charge. I didn't have the best position, I was preparing for a different play, and only saw the defender get hit in the torso, so I took a chance on a player control foul, and tried to sell it. The offensive player's fans went nuts, not your usual fan craziness, but enough craziness to give me pause, so I knew that I had probably screwed the pooch. The offensive player's coach gave me a pass, I think because he was thirty points behind in the third period, and decided to pick his fights.

After the game, I asked my partner about it, and sure enough, the defender was moving toward the offensive player at the time of the wreck, so I blew the call.

Despite this situation, I will still make educated guesses if I have train wrecks. With a whistle, you, at least, have only half the gym against you, and you're letting the players know that they can't willy-nilly bang into each other just for the hell of it, putting their own safety at risk.