Normally a book that I would recommend to learners. I can only say that I am shocked. All of the instances of 'how' cited here are indeed adverbs.
Although 'how' as a subordinating conjunction tends to be restricted to informal usage, in common with the vast majority of subordinators, it introduces adverbial clauses, as in
Do it how you did it last year.
(= more formal ...as/the way you did it ...)
You'll note that all of the subordinate clauses in the dictionary examples, in contrast, are nominal.