Not true at all.
MKG's issue is with his jump shot. That actually is easier and better to develop in the gym (at practice) than in the game.
Do you REALLY want a guy trying to develop a jump shot to do so by continuously taking jump shots in the game? If you answer is yes, then God help you.
His jump shot is not even close to being the only part of the game that needs work. If you think it is... then God help you.
A huge issue with MKG is being able to defend without fouling, that is an aspect of the game that can only be learned through play.
Confidence and consistency are a few more issues that he needs to work on and once again the best place to solve those two issues is through playing.