[just another ref]

Here's the problem with the twist. Defender is stationary, with the dribbler coming straight at him. At the last possible moment, naturally, the dribbler makes a move to try and go around. The defender makes the twist described above. He may or may not move a foot. Trouble is, most fans, and, let's face it, some officials, say "He was moving," and call a block.

Also, on a related note, even if the defender doesn't move at all, some think that if the contact is not centered directly on the torso of the defender and the defender doesn't subsequently fall down, it can't be a charge.