One might suggest that you can't practice the new "tricks" until you've learned them. As for why is it different than weapon skills - it's pretty easy to go to the casino and pay for the next level; but the weapon skills only go up with an increase in dexterity so the ability to learn beyond 100% is considerably more important to the game.
I was mainly concerned that I was doing something wrong, and that I could be taking advantage of learning beyond 100% on stealing/robbing - but since V mentioned in chat that it's supposed to be that way I'm satisfied.
