Those folks are using a version of the punch that works in that context. When the mechanics of the punch are used in sparring, they don't differ hugely from the basic mechanics of a boxing punch. I still use the same basic mechanics I've always used, but I don't look a bit like what you see in any of those drills. I look more like a boxer sometimes (when I'm not standing too tall for boxing movement).I think the thing here is that some of us feel the mechanics it builds are suboptimal, to put it mildly.
This could be why the only place you see punches like that are in point karate and tkd, and they are tip taps.