First of all, I said his shot blocking stinks.
Secondly, if you watch Raps games, you know that his defence is not that good.
Thirdly, his boxing out skills aren't superb, so strong rebounding is pretty generous. He still gets double-double because he plays PF and he gets a lot of minutes.
Lastly, if you look at how he gets at 20-10, it's mostly jump shots. I mean, if you take that many shots (last couple games, he shot a very low FG%), you are bound to score that much.
Anyways, forget about my rant. I know many people still think very highly of his skills.