This is true and unfortunate. Almost everything we know about psychedelic-assisted therapy has come from indigenous practices that have been westernized and appropriated with little credit, recognition, glory or money going back to the original sources of this knowledge and these techniques.
If you read the book, which I have read, it reads like a pantheon of white men getting the credit for all of the psychedelic research that's been done in the last century. Unfortunately, this is often how we determine what's important: Did white men discover it and are they talking about it and publicizing it? That's exactly what we see with Michael Pollan's book.
To your point, he is not an expert in psychedelics. He's not a clinician. He doesn't have an MD or a Ph.D., but he gets a lot of attention because he wrote a best-selling book.