It's because "RC" is not a category of drug. The only reason a given drug is considered an "RC" is because it hasn't had as much of a history of use. An RC stimulant is still a stimulant. An RC psychedelic is still a psychedelic. And people who use RC psychedelics are going to want a different type of discussion than people who use RC stims, or RC opiates (which is why people post about RC psychedelics in the PD forum). LSD was an RC at one point, so was MDMA.
I think we should encourage less distinction between "RCs" and classic drugs, because there is way more similarity between, say, meth and 2-FMA than there is between 4-HO-MiPT and 2-FMA, or between even, say, ethylphenidate and 2-FMA. Although there are additional risks with RCs, and we should be sure to communicate that, making them a separate category encourages people to think of the classic drugs as all safer, when this is not true.