With the caveat that I have neither played any of these games nor read much more than the article you linked above, it sounds as though some of these LARPs are what a different crowd would simply call acting exercises or dramatic long-form improvisation, rather than some totally new and never-before-seen art form.

I played in my first sitdown session of "Final Girl" yesterday, and had a related thought about that. It's experimental, and different, and I definitely had fun. But it's billed as an RPG, and while it may be Role-Playing it's not really a Game. It's more of a storytelling exercise. (Super-condensed description: you portray characters in a slasher movie, but there is no GM and the players all collaboratively decide who/what the killer is and which characters die. I enjoyed it, but there's no "game" per se; the players' only goal is to have fun and tell a good story. As such, I'm not sure it really belongs in the same phylum with traditional RPGs.)

Not that there's anything wrong with any of that, of course, and there's no reason that the word LARP must encompass certain things and not others. But I wonder if it's at all useful to continue using a word so broad that it encompasses both boffer-fests and "Fat Man Down".