those are those kipping pull-ups they do, which is another exercise I don't see the point in since it basically defeats the purpose of a pull-up by using momentum to complete reps.
Exactly why you're expected to do more reps in a faster amount of time. Plus, if I was holding on to something like that IRL trying to get up I would use momentum and not try to do a normal pull-up.
I still don't buy into Crossfit and the insane pricing, but people (not sayin' you specifically) seem to hate on it just because it has gained popularity within the last few years. Just like every other form of fitness there are going to be idiots e.g. personal trainers. Most people don't even know what Crossfit is before they start hating. Anyway, for the money I'd rather join a bouldering gym or something cool. $150/month is ridic for Crossfit, but hey some people need that motivation/direction like a personal trainer.
People don't dislike it just because it's popular. There are some great articles online from some really well known olympic/powerlifting coaches that point out what's wrong with it, and a lot of it has to do with the fact that people pay to get certified as a CrossFit "coach" just to capitalize on the popularity and open a CrossFit gym, but in reality they have no business coaching people and have no real experience doing so. Personally, I think what they have these untrained people do is dangerous, and that Revival Strongman video is a perfect example.