No kidding. It was purely an endurance exercise... and not one that I myself would choose to do, but the point was that nobody's elbows were injured. I definitely wouldn't recommend doing huge numbers like that and snapping them out absolutely as hard as you can. That would be pressing your luck.
Nowadays I do more work with resistance bands. I find it both more productive and easier on the joints as well.
I think he was pointing out that it's probably a combination of power strikes and locking out the joint that causes the damage.
I have done this to my knees with kicks, and I agree, it sucks! My elbows...well I'm a bit of a genetic freak and my elbows are double jointed...so if I fully lock out, I'm punching the guy next to my target..:rofl: I do find this is uniquely helpful in grappling though...I'm pretty hard to arm bar!