The first time I heard about this was from this article: https://www.srf.ch/kultur/gesellschaft-religion/jagd-auf-alte-buecher-ki-firmen-kaufen-antiquariate-leer-und-vernichten-die-buecher

A translated quote from it:

“Not rarities, but the exact opposite,” the dealer reports: “What specifically was bought were nonfiction titles from 1970 onward with ISBN numbers—dusty, unsold stock that no one had wanted for years. Resale is completely out of the question: The books are worthless, and for each title only exactly one copy was purchased.”

That article still tries to frame this as “Rare antique books are going to be lost forever”.