Watching his videos at 0.25x speed is an experience...
Almost all of his tricks look like some pressure variation because he doesn't flick at all. Most of the time he just kicks his foot straight downwards or out of the way. Leaving his nose totally untouched. It's either that or the foot leaves contact with the deck only to kick it down a little bit later. That's why he doesn't have pop and a lot of his tricks look rocketed.
His legs end up being super close together during tricks. As of a medical reason, I don't think there is any. But if I had to say, maybe he can't spread his legs to far apart.
Edit: Or maybe he has shit ankle flexibility.
As an example, two kickflips down a gap at his highest points, one by Jeff the other by Kader.

