I've conducted tests in the gym with simulated knives and airsoft guns. I would say that the video is correct but at points actually underestimates the distance. Anything under 20 feet and I would rate the knife as more dangerous. So stay 25 or more back for safety sake. I've worked with police departments that say 30 feet distance should be maintained and others that say 20. The more the better if dealing with a knife. I personally prefer several blocks away but hey.
I said it in another forum but this brings back into account my opinion that the only useful weapon is one that's already in your hand. Somebody on here said it's amazing police don't walk around with their guns drawn all the time. The truth is that would be more effective. It's also why I talk and train so much in deployment and why my hand rests on my knife most of the time.
+1 on pretty much all of the points you made.
Also, there is quite a difference between the distances police train and generally try to engage knifer's at compared to civilians and what happens in that reality. The knifer is almost always going to get into conversation distance with a civilian before the "pop goes the weasel" surprise and it's usually on their terms. At least police engage on their terms for the most part. Civilians usually engage on the bad guy's terms which negates presentation of a gun at 20+ feet. Awareness may lead to suspicion of a bad guy if he's headed your way but unless his weapon is already out, he's an unknown quantity, a stranger. So, civilians are faced with assessing strangers and deciding: A-Turn tail and leave or B-Establish or submit to contact (warn away or be pleasant). Option C-Draw gun, doesn't come into play at the 20+ foot range.
The tactical folder supporters will like this next part.
I wholeheartedly agree that having a weapon in hand in advance is of the most benefit to survival and for civilians I would place that right under awareness and avoidance (unlike police and the "duty to act"). I also spoke about this on another forum back in 2004 and I actually made a YouTube video about it recently.
It's just a matter of finding a weapon that you can do that with (depending on your laws) as a civilian without brandishing a weapon. Law enforcement may present firearms when dangerous cues are present but civilians cannot. That being the case, in my state and locale, I advocate resting the hand on the knife (FOLDER) but if feeling uncomfortable about something/someone, drawing the knife into hand (DISCREETLY) from where it can be opened and used if necessary. Follow-up would be the same as the standard stranger reactions, only you have a "POSSIBLE" weapon already in hand: A-Turn tail and leave or B-Establish or submit to contact (warn away or be pleasant). If something pops off, you already have 75% of deployment covered. Doesn't get much better then that.
One could always wait for a stranger to brandish and attack. Then one could try to index and draw a weapon from concealment. Unlikely and yet widely taught. Anyway's that's my 2 cents. Your results with that approach may vary. In my state and locale it's o.k., in yours it may be brandishing.
Even if you disagree with that approach, there isn't anywhere that a civilian can walk around with a fixed blade or firearm in hand without having brandished a weapon.