Kobe's like "Dayum! That cracker can dunk?!?"
Well, in all seriousness, yes, he can, as answered by a lot of the other posters here. When you're 6'8 and have a standing reach of 8'9, you don't need too much vert to be able to dunk the ball in. Dunking is said to be pretty tiring, although with all the people he's tasked to defend, I doubt he's too tired. It's probably just not his style to do so.