He did a handful of bad shit there... from landing too deep, staying too much on the ground to not having his arms to his back before landing (which in turn made him lose a ton of time on the ground).
Yeah it doesn't make too much sense... maybe that % allows you to be explosive enough and at the same time it's still very heavy so the power output is the highest? I don't know.
By the way - when it gets warmer outside I'm going to try and jump with a weight belt on. If the weight belt gives me a boost in terms of strength in the squat, I'm going to see practically if that's due to better bar stabilizing or if it's also a matter of muscle irradiation with the leg muscles contracting more forcefully due to the core generating more force by pushing into the belt.
I know the vast majority of people around here will laugh at this ^^^ but I'm going to see it for myself. Not sure anyone tried this in the past (jumping with a weight belt on). The downfall is it's weight but I'll try it nevertheless.