I think it took a lot of guts, humility and concern for fellow shooters for Tex Grebner to take the heat just so others can learn from his unfortunate nd and I applaud him for it. And, yes, he was certainly culpable to a degree for shooting himself and I can't see where he's ever said otherwise.
As a requirement of my job for thirty years, I wore a handgun of one kind or another in one kind of a holster or another for just about every day of those thirty years and never did find an occasion to shoot myself or anybody else that didn't need shooting. From a flap holster covering my 1911 while serving in the military police for four years to a Bianchi snap-open thumb break I was wearing at the time of my retirement, I've had experience with a variety of leather and have long understood the importance of using a well-made holster that holds your weapon securely while allowing instant access to the gun. Unfortunately, like so many other things in life (canoes and photography come to mind), there is a "law of reciprocity" we all have to reckon with when choosing a holster-to get one thing, you'll have to give up another; to gain speed of draw, you'll have to give up a degree of retention security and vice-versa.
I've looked at the videos provided and have read the many posts in this thread and to me, though I generally loath blaming the arrow for the Indian's (oops, I mean Native American's) mistake, the conclusion is inescapable: the Serpa is ergonomically predisposed to abet an nd. It's an unforgiving design that might work fine for those willing to put the obligatory training time into adapting to its idiosyncracies but I can certainly understand why trainers are reluctant to have the Serpa worn and used by students and trainees who, almost by definition, are not so well trained.
The Serpa seems unnecessarily complicated. Why use it when there are so many other simpler and intrinsically safer designs available?