The argument is meta used the book so the LLM can be considered a derivative work in some sense.

Repeat for every copyrighted work and you end up with publishers reasonably arguing meta would not be able to produce their LLM without copyrighted work, which they did not pay for.

It's an argument for the courts, of course.

The argument is whether the LLM training on the copyrighted work is Fair Use or not. Should META pay for the copyright on works it ingests for training purposes?

Facebook are using the contents of the book to make money.