Right now, Rox has exclusively used Yao on the low post. We know he has a fairly good midrange jumper. Why not use it? This can cut down his TO numbers. I remembered when Hakeem was around, he made these kinds of jumpers often.
Yao is completely capable of making his high post shots, with fairly good percentage. But I think Rudy T really wants him in the low post. That's where the Rockets really need an inside presence. In the biginning, Yao's low-post game is pretty bad. The coaches must be telling him constantly never to shoot from high-post. They want Ming to be near the basket wheven Rockets shoot so he can get rebound. Yao has improved his low-post game tremendously over the first 1/3 of the season. Hopefully when he improves more, the coaches would just let him shoot from whever he feels comfortable.