This is a nothingburger. If we were to hold this blog post to the same standard that they expect to hold the book to:

  * The email exchange goes on about a single claim from another rebuttal from the reading of a single chapter that indulges in nitpicking on the interpretation rather than general ideas

  * The WordPress blog, where clarifications were posted, is Matthew Walker's blog and this can be trivially verified[1]. Yet, the author first claimed no such clarification existed and then when directly linked to it, claimed no indication that it indeed was Matthew Walker's blog. Who is being lazy / disingenuous now ? (Note that Walker's blog directly links to Alexey Guzey's takedown).

As an aisde, the omission of a bar that is clearly an outlier (indicating non optimal buckets, rather than invalidation of a trend) and imo is not enough to have the author spend so much time and energy into this, in the absence of malintent.

[1] linked from his website https://www.sleepdiplomat.com/author