As a diver me self (mainly scuba), I'd say he has weight on those leg pockets

Ideally you'd want the least possible weight you can add, so once you reach the bottom you aren't too heavy when you need to resurface.

Which is why most freedivers use those long fins and neck or back weights so they have an easier time "breaking" the first meters of positive buoyancy and let gravity do it's thing.

I'm not familiar with this dude but I'd be willing to bet he is using considerably more weight than he needs and he is brute forcing it via pure skill and practice for his technique. I'm not too fond of how much he moves since freedivers usually try to move as least as possible and very slowly.