No he has not. When a player uses weight to try to back up their opponent, that's the worst kind of offense you want. The player is exerting a lot of stamina and half the time they are off balanced. Unless the player backing up his opponent is prime Shaq, it is the easy to defend as it doesn't induce any help. The result is usually a 30-35% hook over the opponent which is inefficient as you can ask for. The only time it can induce doubles or get defenders one pass away to turn their heads, is if Spurs are playing a dumbass team like the Kings -- but at the end of the day those games are irrelevant.
He does need to lose weight and get leaner so he can have the footspeed to incorporate foot work in situations where he's getting crowded facing up. Getting lighter will help him gain a step and he'll be able to create the needed small, yet effective separation to execute counters from when he receives the ball in Pick N pops or when he receives the ball in PnRs when he's diving. Then again, his counters disappeared last year because he spent the summer again lounging around. Getting lighter will actually help him more physically as he'll be able to aggressively and physically get around his man putting pressure towards the basket. If he's staying the same weight or comes into camp out of shape again, he won't be effective with the ball. He simply won't.