I know that you are responding to Bubbletrubble here, but what you are saying (and the way that you are saying it) cries for an answer. You describe an incident in which a diver got away from whilst, "doing a mask flood exercise, he could not clear his mask, I had a hand on his BC, I saw his eyes go wide and grabbed him before he even started moving, he got his legs under him and we were on the surface of the pool in very short order. There are things beyond ANYONE'S ability to control."
I have to agree with you that once the gorilla you describe was moving there was nothing that anyone could have done to stop him, so it was a damn good thing that you were very shallow water, else the incident might have had a very different outcome.
All that I want to remark on is that in forty-odd years of instruction I've never had a student "bolt" on me. I, personally, would see having that happen, in and of itself, as a serious failure on my part, even if the student was unharmed physically. I would feel that I had not carefully, step by step, each tiny step a success, prepared the student for the performance of the skill; and I'd feel that it was a failure on my part if I did not detect incipient problems and deal with them long before they turn into a "bolt," or, in fact, long before they turn into anything that the student might even see as a failure on his or her part.
Have I avoided this sort of problem just through perspicacity and skill? Probably not, there may well be an element of, "luck of the draw," here. But when I teach I try my hardest to stack the deck in my favor, and that is why I only teach Scripps Model 100 hour courses.