Hence all the AI labs buying up and destroying physical books. Even "yellow press" stuff, pulp fiction, dime novels and whatnot "low quality" literature are a valuable source of how actual humans write.

I wouldn't even have much of a problem with it - if these labs would be fair enough to humanity as a whole to provide the raw scans after the process is completed, and if they would limit themselves to books that have been on the market for more than 20 years.