To me, it is a combination of bad holster design and a bad drawing technique. (and I posted as much in response to his vid)
Putting a release in a holster right near where the thumb safety of the gun is?! Wow. I guess I am not tactical enough to own such a holster.
Thanks for posting this, and thanks to your friend for having the guts to post it and take responsibility for his actions. He may have just saved other folks from the same (or worse) fate.
If that were a hollow point, it probably would've take his knee out, his foot off, or just destroyed all the muscle in his thigh on the way out.
One thing that was scary to me was the shockwave of the bullet going through his leg, which could be seen in the slow-motion shot. From ballistic gelatin videos, we know that shock waves is a lot worse with HPs.
Here's to a speedy recovery to your friend.