I have wondered about the selection bias issue, and I was hopeful that this writeup would give a good look at this and other potential issues with the study.

But when I read it, I was a bit turned off by the author's attitude — which seems to be that he or some of his colleagues should have been consulted by the study authors because they are "statistics experts".

He refers to this apparent omission multiple times, and he also seems to think he's dunking on the authors when he references Theranos (and the fact that its advisors came from government/law/military). But this study is completely unrelated to Theranos (though they both involve blood and Stanford). Off-topic comments like these left me wondering if his analysis is a fair critique, or if he has an axe to grind.