Which reads as "they work, but the people promoting them don't know how".

I mean, the classic example would be willow bark as a pain reliever. I doubt anybody who understood that it appeared to be an effect pain reliever knew much about COX1 and COX2 inhibitors.

That sounds accurate. Plants do have tons of chemicals, some of them may have very potent effects on the body chemistry. Unlike homeopathy where the proposed effect model defies physics, there's nothing implausible here, the problem with herbal remedies may be that ingesting a very complex cocktail of chemicals and thinking "it's fine because it's natural" is not always the best approach. It's usually not easy to properly understand what happens when ingesting such mixtures. Evolutionary, things that are very likely to seriously hurt you have been probably excluded by now, but it's still pretty poorly understood what exactly is going on when you use some "natural herbal mix". So, anybody who makes bold claims about what exactly is the action of this or that herbal remedy, usually is not painting the whole picture.