Have you ever tried to lift like that relying mostly on the elastic qualities of the passive connective tissues of the back and the muscles? I wouldn't recommend it but you'd probalby be able to lift a whole lot more than you think if your back is "healthy". The point being it's not as impressive as it looks because he is simply using the end range of that ability. It will take him so far and he will crash and burn. I try not to be "impressed" by stupid things
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If he tried to get his muscles to fire properly in a way that can be sustained and progressed he'd fail at that and need intervention by a real smart coach. A guy that is all lumbar is not strong. He is imbalanced and weak. And do you think he can squat worth a shit? The point is one really bad but seemingly strong lift doesn't really mean "strong". It's just a guy taking advantage of the mechanical properties of his back and adding a little effort to it. Just keeping it real
I'm not saying he doesn't have a strong back. It's kinda silly to see that kind of thing with a belt though.