Hi, I'm the author of the piece. I cover this objection specifically in Section 14 of the essay. tldr: Walker claims his book is scientifically accurate (I quote him in the introduction), he cites it in his academic papers (see section 14) and therefore he seems to have an obligation to be precise in his language -- some of the book's misinformation has already made its way into the scientific literature. As I note in the introduction, this depression thing is not a single incident (of course there will be slips in a >300 page book), but instead a consistent pattern of exaggeration and scaremongering.
I appreciated the piece quite a bit, thank you. I can't sleep past seven hours anymore and am comfortable if I only get six. I suppose I've felt vaguely guilty that I don't sleep more than I do after hearing many pop science news stories. This eases a bit of worry. I wasn't all that worked up about it, I just always feel like I should really try and get more sleep and and am a little disappointed in myself when I have the chance to put in those golden eight hours and instead pop out of bed to make some eggs and toast. I was going to do what I was going to do regardless of what anyone said so I don't care which of you is doling out the coins of truth, happy to just have some peace of mind.
beware second-option bias. guzey's article is indeed rigorous, as usual, and walker's book seems pretty wishy-washy in places, although i only read reviews. but... sleep is extremely good for you. as the best rebuttal on r/ssc points out, the overall message of the book is correct and shouldn't be overly compromised by lower-level criticisms, however valid