Agreed, mostly worthless fluff. I'd challenge the authors to remove any reference to a study that has insufficient power or that has not been replicated.
However, you don't need to have strong evidence behind a technique for it to be worth trying – if the upside is high enough or the costs are low enough, it could still be worth it.
Well yeah but there's literally 1000's of books like that on Amazon - if yours isn't different, then why bother?