incredible flexibility. I never was nor will I ever be that rubbery
dexterity. it looks like those limbs are kind of flopping around, but every touch is a shove.
You know how people always debate 'active' toes vs 'flat' toes when you're in someone's guard? Flat toes (having your butt on your heels and the tops of your feet on the floor) are for base, active toes (being up on the balls of your feet with your butt on your heels) are for passing...
How to Use Your Feet to Maximum Advantage in Jiu Jitsu
in this article they call it 'ballerina feet', active toes, and frog feet
Rener curls his toes so far that he gets 'active' toes in the 'ballerina feet' position. Hard to describe, never seen anyone else do it. instead of being on the balls of his feet, he's on the first knuckle of the toes. But where it looks like his feet are 'base', they're actually always 'pressure'.