Millions of books go in the trash every day. Should all private property come with such an asterisk that it ought to be preserved for whatever unlikely contingency you can imagine? I don't know, AI actually seems like a much more worthwhile pursuit.
They don't care about the R.L. Stein Goosebumps series or Louis L'Amour pulp fiction. They want the stuff that isn't digitized and they're willing to destroy original artifact to do so with no guarantee that even the digitized text will ever be made publicly available.
It's foolish and selfish.
That was something that someone on Twitter made up and then got quoted in an article. All of the books being scanned have ISBNs, meaning they're from 1970 or later. The books being sold off are rare in the sense that there aren't many copies in circulation, but they aren't priceless artifacts. If they were, they'd be being sold individually at high prices by boutique booksellers rather than being sold by the pallet by wholesalers. It's going to mostly be stuff like "The Best Places to Eat in Milwaukee, 1992 edition" or "The 2006 Guide to the Stock Market" or "Teach Yourself Visual Basic 3.0 in 28 Days".