I agree that the issues

• whether AI output are derivative works of its input, and
• whether input to AI is fair use and requires no compensation

are separate, but I think they are related, in that AI companies are trying to impose whatever interpretation of copyright that is convenient to them to the rest of the society.

And indeed Meta pirated books to feed its AI.

https://www.techspot.com/news/101507-meta-admits-using-pirated-books-train-ai-but.html