My understanding is that fear of not being able to fall asleep often contributes to the perpetuation of insomnia. So while the recommendation of CBT-I might be helpful, if the book also increases someone's fear of not being able to fall sleep (or more specifically fear of the consequences thereof) it might be net unhelpful. As an analogy, imagine a book that recommends exposure therapy for arachnophobia and also describes in detail all of the ways that spiders can harm humans. Something that provides the recommendation without reinforcing the counterproductive fear is probably more appropriate.

He literally calls out exactly that problem as an “ethics quandary” for approaching this problem. Informing people of the risks can increase the risks. What do you propose he does differently? Just not talk about it at all?