I just registered to offer some perhaps not readily available information which may be relevant to your evaluation.

I heard Dave Grossman speak in person when I was in the Marines around 2005. I remember his emphasis on getting enough sleep, and less than 30 minutes at a stretch not being worthwhile, but I mostly remember my impression of a fanatic. By this I mean he did not come across as a rational person committed to introspection and careful evaluation of his own beliefs. The general opinion of a bunch of Marine combat veterans was that he was way too wound up and seemed on the verge of a nervous breakdown.

He started his talk with a story about how he won't take his granddaughter for a walk in the woods without his German Shepherd, a folding knife, and a concealed handgun. I can't say he's wrong, but I can say that whatever motivates Dave Grossman seems to lead to a view of the world that is very distant from what I think are rational behaviors.