Completely agreed that there are plenty of homebrewers out there who are so-called "supertasters"; as a matter of fact, one of the best tasters I've ever seen is the wife of one of my homebrewing friends, and she knows little about brewing and is not a member of the BJCP or Cicerone programs. In my experience (I have organized a weekly group that focuses on BJCP tasting exam preparation for about 2 years), tasting regularly, as well as using off-flavor kits and in my case brewing off-batches, does very much improve the palate. I'm not saying that one must be a member of one of these groups to be a good taster; however, it does lend a lot more credibility to the experimental results. These evaluators used for Ray's experiments may be good tasters, or may not be, meaning more uncertainty and less significant results. To give some credibility to them, I think credentials would help.
Therefore I claim that, no, I am not assuming you can't taste off-flavors because a person is not a member of one of these organizations; I am assuming the converse, actually, which is that if one HAS become a member of one of these organizations and been certified by them in some way, then that person's tasting skills are perceived as more trustworthy. Isn't this why these organizations exist? So that you can have a reliable, experienced individual evaluate your beers, whether in competition (BJCP) or on tap at some beer-serving establishment (Cicerone) where you have uncertainty in your own judgment, or just less experience? For me, if there were some credentials given, I'd have much more confidence in the triangle test results in all of his experiments.
I think the best thing about his stuff is that, like I said, it has inspired both me and many members of my homebrew club to do very similar types of controlled experiments but on larger scales (multiple controlled batches) and I hope that it does inspire others to do the same. It's a lot of fun.