Interesting you should mention this. I don't kick this way, but, for as long as I can remember, I've been able to stand this way (toes curled under on both feet). When I was a svelt 21 year old
I could even jump up and down on concrete with my toes in this position. Very strange. Last I checked I can still walk around like this on a soft surface (grass, gym mat, etc), but jumping jacks are out of the question.
I may have to start developing this talent out of the realm of "party trick" and into the realm of kicks.