Dude, against the Thunder, Diaw was almost always being guarded by smaller guys, so off course he was going to play in the post. Diaw is a brilliant post player. His BBIQ plays into that, but he's also very bulky -- much more bulky than Anderson can really ever hope of being. Diaw's versatility lies in the fact that he is extremely agile for his size. Anderson is extremely unagile for his size, and his body type makes him a poor post scorer (for the same reason that plague's Durant). It's really hard for anyone who's tall and skinny to back someone down, because they lack leverage. The same reason why Green was able to stonewall Durant in the post in the WCF is why Anderson could be shut down by pretty much anyone is that's what made or broke his game.
Of course it does. That's like saying ballet doesn't require athleticism. Balance, coordination and agility are things that Diaw has from his time as a small. And they are invaluable to his ability to get around bigger players. I agree that shooting is critical to Anderson's ability to score, because he's not going to get a ton of layups off the dribble. But
Diaw's 6-9 with great post instincts. He was always going to be a forward in the league. But you're dead wrong on his lateral quickness. He used to be a perimeter defender, which is something Anderson doesn't have. And he's still very good at hedging and switching. Anderson being 240 or whatever won't do anything but slow him down more. He won't have any advantage anywhere on the court. Right now, he's still taller than almost anyone who would guard him, which is huge for someone on the perimeter. He can shoot over his man. If he had to play against PFs? No. And he wouldn't be more agile than them, either. And he couldn't have Diaw's base. He really would just drop out of the league.