Haha. I dunno man, TA doesn’t exactly seem like a marketing snake-oil salesman kinda brand IMHO. That amount of flex clearly does… something, to how the fin reacts to the water. The resulting effect may not be for you, or everyone, but people have been using the greenough power blade single fin for years and seem to like it. It’s been much discussed here in the past (along with the tomo hatchet fins). Never tried one myself but would be curious. I found the “spring” on the krypt hatchets (tri or quad) too unpredictable to spend much time messing around with different setups.
Flex absolutely impacts the performance of the fin. No question.
How it works within a fin cluster.... Probably less so