Actually studies have been done on rhodiola. Also, you're saying that if something worked it would be banned, while at the same time saying coffee works and it's not banned, so you're kind of contradicting yourself, friend. What's it to ya, anyway? Why do you care?
He is right though. Researches for some reason tend to exaggerate subtle or barely existing effects, and are misleading. For example, fact that Rhodiola is well researched gives an illusion it should really work. While in reality it is either placebo or has very mild effect.
Then you have something like Phenibut or 1,3 DMAA, barely researched at all but definitely works. Everything that works can be dangerous and is usually prohibited and regulated.
Reports about herbal remedies working strongly are placebo effect and exaggeration.