Think about...people who play softball well have spent countless hours tossing a ball back and forth...probably starting around 2 or 3 YOA. They are trained how to determine the final location of the ball based upon the speed of the ball, the release point and the release angle. Seriously, how many thrown balls has a good 16U player caught? My guess is a couple of hundred of thousand.
So, when a ball is thrown which does *not* fit the pattern, the brain has trouble figuring out the location, and gets confused. Only skilled batters can consistently hit the rise and the drop.