They're not saying "one point" about the conclusion, they're saying that their statement isn't nearly confident enough, and that they would prefer that they say with strong confidence that there is unequivocally NO positive effect on cognition.

It is a hell of a thing for a random person on an internet forum to be so unilateral, without providing some kind of strong evidence (aside from statements about "the industry", which is kind of beside the point). I would also suggest if you want to be so unequivocal, that the burden of proof is especially high for you.

This "point" isn't actually all that rational - it's knee jerk skepticism. It's a fine default for yourself, but it's not something you get to force on others because they admit there's room for the potential of benefit.

Again: You're perfectly fine to hold that opinion yourself, but when you start trying to force that on others - you now have an especially high bar to reach, and yes - being a lead researcher in the field is exactly what I'm looking for when someone says "X has been proven to not have a benefit for Y".

"Trust me, I'm a scientitian" - Not sure the point of that juvenile wordplay, but Ok: we do have these things called scientists, some are good, some are terrible. You still need to back up your statements - that's the key part, this isn't a blind appeal to authority. And it's a hell of a lot better than "Trust me, I'm a nerd with very strong beliefs about a topic I know very little about".