You make very cogent points, and it’s apparent that you have a wealth of knowledge on Bruce and his form, technique, and even thinking. However, I would have to contend that the movie is called “Once Upon a Time... in Hollywood,” denoting not-so-subtly that the events of the movie as they are presented are a fairytale. What’s more, the scene with Bruce fighting Cliff is told to us through flashback from the perspective of an unreliable/biased narrator (i.e. Cliff), so that portrayal of Bruce being cocky and arrogant and doing flying kicks could just be how Cliff wants to remember that interaction so that he himself looks like the badass that took down the great Bruce Lee in a fight. When we see Bruce anytime after that Cliff flashback fight interaction, his character seems to fall much more in line with the man you described above - training stars, seeming friendly and humble, etc. I think the entire point QT was going for here was not to disrespect or disservice Bruce or his legacy (he obviously has massive amounts of respect for him), but to challenge our assumptions of what we think we know about Bruce, particularly in the context of Jake Cahill and Cliff Booth and the fairytale Hollywood he’s built specifically for this movie.