Tucking their front legs and extending their back legs wouldn't seem to gain anything. Then, rotating the front of the body would seem to involve opposite rotation of the back.

However it's done, they seem to be able to both induce a rotation and stop it. At will, and fast. They don't seem to be able to level their feet if they are dropped, say, feet first, so it would seem to be a torsion thing with the trunk.

Now, my cat knows how to do this. And I can't completely figure it out. Not only that, it seems so complicated that if it were me, by the time I started to think about it I would have landed with a very large "thump" on my head or butt or something.

I've always known the darned thing knew stuff I didn't. Where it goes during the day, for instance. Or, where it goes at night. What it's thinking. Why it ever moves. How it purrs.

Oh, well.