I am very disappointed in Matthew Walker. In fact, if I were working in the same field as him, these findings would cast a doubt on most of his other work. The density of the errors almost makes me unsure which is worse: the errors are unintentional due to carelessness or they are deliberate to create a better sounding story. (Of course, the latter is worse as it is basically academic fraud.)
I believe there should be more books that are scientifically sound, yet accessible to most people. I thought this was one such book, but alas.