I don't know if he's actually leaning that way, or if it's just because he has his shoulder back so has quicker and better access to his gun. I think he's trying to appear intimidating on the video, so he has his hand resting on his service weapon, and that's why it looks like he's leaning.
EDIT: No, you're right. He is leaning. He has all his weight on his right leg and his left leg is bent. Who knows?
