Basically the instruction most benefits people within +/- 3 sigma from the mean in terms of athletic ability...e.g. most people. For the outliers (either positive or negative) it won't do much...
Not sure what that means. I'll cut to the 'chase' I believe in instruction. It will shorten the 'learning curve'. I have always given my DD & DS additional instruction. If your DD can't hit the ball the game won't be fun and they will not want to play anymore. It's as simple as that.