This guy sounds like he is just really excited to be Celtic, but he is being smart and trying to secure his future as well. Being young, he certainly is 'talking the talk', I think that is simply a matter of a kid who realizes he is about to finally 'make it' and is really wound up. I think he knows he can play in the NBA and that has been his dream above everything else through good and bad. Now his dream is about to come true.
I know I would be talking a mile a minute and be just as excited if I was his age and in his position. Here he is, about to join the World Champion Celtics. Who wouldnt be excited?