That's a reasonable take but still depends on the trials. E.G. if the blind trial was 20 college age Americans males, and the non-blind trial was 1000 people from various ages and countries, I'd probably lean towards trusting the non-blind trials (unless I happened to be a college age American male).

Or if all the available trials are n<=20, I'll probably lean towards trusting the anecdotes, at least enough to try the supplement for myself.

When it comes to cheap-to-produce supplements, very limited trial data is the norm, unfortunately. There's no money for running large trials.