I think it's a bit like lifting the bar, eh? You wouldn't teach a total beginner to squat 300 pounds, you would first do it with nothing to get their form right.
Or like learning words in a language. You can jump in with pimsleur method and learn whole sentences at a time, but you'll never develop mastery (a bit like a pure brawler who learns no technique could be good, but will hit a threshold).
Learning the meaning of each word (posture/technique) at a time, and sentence structures (how to put postures/techniques together coherently) is like learning from a compliant or semi-compliant "demo."
A lot of language learners know all the words/meaning involved, but when someone actually natively speaks that language, they have no idea what any of it means because they've never heard it or been to that country.
Like that, a demo can serve to familiarize with the language and form involved.
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Of course once pressure is applied, you might have a bit too much weight on the rack and squat slightly off balanced and have to get feedback to fix it. Or that pressure might be travelling to that country and talking with native speakers, you might speak horribly jumbled, but you have a foundation to build on.
Then we have demo's like OPs, which are strange sounding sentences. They seem to work when written (demoed), but we don't have evidence anyone actually speaks them (in real scenarios).
The irony of you posting this is manyfold.
1) Despite their full intensity, some of their moves can't be serious (
e.g. guy choking from behind and she just flails her legs and he falls down). Or she knees him and he just over repeatedly falls. I feel like this demo is worse than OP's because this type of training might actually mislead someone into thinking their moves are going to work in a real environment if all their partners just buckle and don't strike back the entire time.
2) If you watch closely at this time in the video you'll see the move that OP posted (at least a better application of it)
https://youtu.be/S3drZ6bURUs?t=1m9s