Deadlift is a POWER MOVEMENT. As long as you do not bend your knees and use your upper legs as an assistance during movement it's all good.
He does deadlift with speed like this because he firmly believes that SPEED is the key.
HE IS NOT A BODYBUILDER FOR FUCK'S SAKE, WHO GIVES A FUCK ABOUT WAIST? He has top3 deadlift in the fucking world, anyone who shittalks about his waist is fucking homo, no offence.