bettas are from southeast asia. long finned colorful varieties would probably die of exhaustion or get eaten before they were able to reproduce in water like that. notice how the bettas always appear at the feet of the cameraman. my guess is he's just putting them there before the guy with the net 'finds' them. that many randomly colored fish wouldn't happen to appear under rocks in an inch of decently flowing water. judging by the erosion on the hill next to them, that stream's been there awhile. not to mention the one at 2:33 wasn't even in water
even if they are released by other people, those must be some unhappy pet owners if they're all releasing enough bettas in this one stream for these guys to be going out looking for them. and again, the fish can't even swim in the video, no way they're reproducing.
oh and I did go through and watch some of the other videos, definitely fake.