The difference is that when the robot reads that book, it maintains a verbatim copy of that book as part of it’s training material indefinitely and can reference and re-reference that material infinitely. That is not how it works when a human reads a book.
The ‘copy’ that the AI retains indefinitely is a verbatim copy of the original work, and the entire point of “copyright” is to control how and where copies are used.
Yes, there are ‘fair use’ exceptions to copyright. I don’t think you realize it, but your argument is less about whether this violates copyright (it absolutely does under the textbook definition) and more about whether there should be a fair-use exemption for AIs; you seem to think yes, I would disagree.
I’d also argue the AI example qualifies as it as ‘derivative work’ based on the original, which STILL would require honoring copyright laws and compensating the creators of the original works. Basically, before reading the book it was just “AI”. After reading the book it has become “AI + book1”, a derivative work, and on and on and on.