High kicks for me is anything above my own hip. I agree with your idea about primal moment, and in most of those moments the knee does not go higher than the hip bone, in the case they do the moments where not "snappy" but "pushy". I learnt the lesson the hard way, I used to be a kick boxer for more than 7 years. All those high kicks ruined my lower back and knees. Anyway you slice and dice the argument it will be inconclusive, so why take the risk of a high kick marital art when there are a lot which do not include these at their core ? (Unless of course you have problems in your arms) Anyway, you would not want to use high kicks for your self defence. They are nice to watch on movies and in ring fights but I would not take such risks in the street.