I think in the tech industry we get caught up on 'novel' and 'new' because duplication is cheap to the point of almost free.
I think you might be in trouble there, a number of savants have been known throughout history who have been able to learn various things with no instruction and simply by hearing or seeing a work done by someone else have been able to recreate it or produce something in their style.
Part of the conceit of the story is that even a mechanical copy of a known work can become something else because of the inner experience of the person reproducing it. Menard's Quixote, his fictional author thought, was different because Menard knew things and lived through things that Cervantes before him didn't, and so the exact same words are injected of different connotations because of this.
It's absurd, but it explores something about authorship.
ChatGPT and AI have no inner lives, no authorial perspective, and so they cannot use this defense. In their case, a copy is truly "stolen" with no additional value.
Even after following along and gaining the confidence to paint on their own, they continue to use the same approach to painting. Are those paintings afterwards derivative works and to be treated the same way as an AI painting asked to create a scene with certain elements in the stye of Bob Ross?
The AI is learning. Why is one of those things stealing and not the other?
The definition of a derivative work is agnostic to the means to create it. The final product is what is being evaluated.
If the answer is "but the Bob Ross paintings that are derivative works by amateurs are never sold and only hung at home - it would only be an issue if they sold them or tried to display them publicly as described https://www.law.cornell.edu/uscode/text/17/106 " - then I would agree.
If I create an image through any means - be it paint on canvas, stylus on tablet, or prompt and ML and don't violate 17 U.S. Code § 106 then there shouldn't be any issue.
If, however, I publish that image - again, no matter how it is created - then there is an issue. But it isn't the maker of the paints, or Adobe, or the creators of whatever ML model generated it. A program cannot hold a copyright and cannot itself create a derivative work. ( https://www.smithsonianmag.com/smart-news/us-copyright-offic... ) and so the issue of creating and publishing a derivative work is upon the human who did it - not the computer.
If you want to sue someone for publishing an image generated as "create a landscape of San Francisco in the style of Pixar" then have Pixar go after the person who published that image. It doesn't matter what process created that image.