He had the collision because he was not in control of his body. If the ball comes out under these circumstances, no matter how long it had been held previously, there is no catch. Check out the definition of a catch for more details. The batter's wrists broke. Maybe, but not always.
Umpires look for control of the barrel of the bat.
If the batter loses control of the bat barrel, we have a strike. It may be that a check swing appeal turns a ball into a strike. The appeal to the base umpire should never turn a strike into a ball, since the plate umpire should not be calling a strike unless sure that the batter swung. On the contrary, the opposite is usually the case. Most instances of interference are the result of undesired, accidental contact between the ball and an offensive player or between an offensive player and a defensive player.