Having height only effect training creates some counter-intuitive relationships in the game engine, but if works for this model/simulation or at least better than trying to incorporate it into both training and after the fact, into the game engine.
In real life, there are a number of attributes that might be physical constants that would effect a players performance: height, speed, wingspan, weight, width etc. But its a question of how deep should the simulation be.
Also, perhaps you've never seen a 7' 6" player that can't block a shot, because you've only seen player that height in the pros. But when I was in college, we had a player who was that tall (they took him as a project that they thought would develop, but he never did) and he was very uncoordinated -- his ability to rebound and block shot was minimal at best.