alt Hacker NewsBill Pollock (who is nonstarch press) is a very serious editor so I would not worry about that with NSP books.
Of course it’s a small operation, and so isn’t under the same pressures of a big operation. When you’re a boutique operation your only differentiation is quality. Your rule of thumb is unfortunately probably pretty good in the general case.
The editor is not the one producing the text. For this book, the sample chapter seems to make heavy use of LLM output. Pangram agrees. I guess that for books about AI it's fair game? Eat your own dog food so to speak. People who don't like AI are not the target audience.