< You’ve basically described what the authors did.

Not at all. The criticism is that the authors didn’t perform the analysis at a consistent time point after sample collection or account for the different times in their analysis. I described an analytical method that would fix some of those concerns.

> Collecting and possessing wild Psilocybe isn’t very legal for most folks or labs in most places.

I’m not sure how that is relevant. The people involved in the study are already collecting these samples, so either they are licensed to handle controlled substances or don’t care if they are following the law. Either way, they should standardize their sample collection methods or not run the study. If they can’t run the study correctly then they shouldn’t perform the study.

> On top of that these mushrooms don’t just grow everywhere. Or at the same time. And they’d would all probably need to be sent to the same lab.

Somehow, other scientists have been able to run these analytical studies correctly. If it is not feasible for the authors to use the correct procedures then that is a good reason not to attempt the study.