Love your video. I haven't finished the whole thing, but I will.
I did knife / stick fencing for years and still mess around with it. We'd watch videos like yours and do a lot of sparring with BJJ / kickboxing rules and weapons.
My takeaway from all that time is that there are basically three kinds of opponents:
Untrained, Athletes, and Fencers
Untrained people with a knife are basically ineffective and I can just run backward from the jabbing.
Athletes are dangerous for just the same reason you showed. I'm not a champion at grappling. I'm like a middling no gi gym warrior, and I find controlling a knife arm of even an untrained athlete completely impossible. My highest percentage move for beating them sparring is the same as the one above: run backwards while throwing straight punches until their personality changes.
Against fencers, if they are bad, sometimes you can do a fencing trick and they'll respond to it because they are basically trained to give up when you do a trick. But if they are athletic and good, there is very little you can do without a weapon other than use power punching to try to knock them out really fast, which is always the best technique for anyone who is 100% outclassed. Again, impossible to grab their hand.
I suspect that you, as a grappling champion, may have access to techniques that most people do not have access to. I don't know what it is like to be you. However, for me, after years of kali and bjj, and kick boxing, and being big, and having big hands, and an average deadlift, I do not find it possible to control the knife arm of someone much smaller than me if they have any athletic attributes or training.
I think maybe all the fencing stuff I did gives me a greater than normal ability to back up and jab from a knife because it isn't mysterious to me. I can read people with sticks and knives pretty well, so I can throw jab against it. That might be hard for someone who hasn't fenced because they won't know how someone does it. You also have to be able to throw pretty hard punches while backing up like karate people do.
Edit: tl;dr: if someone told me that they are afraid of being attacked with a knife and wanted to learn to defend against it, I would add sabre sparring to their regular MMA routine, and then move up to mismatched weapon sparring later. It's actually fun and it is possible to get better at it. But I wouldn't attach a prescription for best moves. I'd just let them do their MMA stuff, but if the gym teaches people how to walk backward while hitting, I think they will find that's the best move.
If you turn around and someone is already knifing you, it is too late to grab the knife hand because if you miss once or twice, they will keep stabbing. The better move is to just acknowledge their stationary, unguarded face, and knock them the fuck out.
