Knife attacks are fearful things, and someone can drop dead, right on the spot. I guess everyone knows that by using common sense.
That is something that any knife fighter needs to answer, which is, what will I do to save myself?
I mentioned in another post, that killing is easy; but the fighter needs to know that for himself. In a real fight somebody might die, either you or the other guy. The deadly aspects of it, are as serious as gun fighting, just closer in.
That conundrum is up to the fighter to solve. Because if you underestimate your opponent, he may kill you. So pick the system that teaches defense more than offense, IMHO. Escape and evade.