Even the fair use argument is putting the cart before the horse. I would think these plaintiffs need to convince a court that the works are derivative first, and iff they are derivative, then the fair use argument can be made (that the reproduction is not a copyright infringement, {because e.g., the result is substantially different from the input}).
Asking "is it fair use for a [human/computer] to [study/be trained on] copyrighted works" simply does not make sense as a fair use question because the answer has always been "looking at a painting and internalizing it has nothing to do with fair use, of course studying the old masters is permitted." I'm far from convinced the answer should be any different here.
So to me they're barking up a non productive tree by trying to essentially say "the entire model is copyright infringement." Hopefully a judge/jury is not convinced. IMO it should be case by case for any given artifact, whether human or machine produced, does it infringe. Obviously a harder hill to climb for the plaintiffs.
A lot of people also conflate plagiarism with copyright infringement. There are a lot of ways I can plagiarize--or at least create works that obviously draw very heavily from other work without attribution--that may be very frowned on, especially in an academic setting, but are not actually infringing.
Copyright defines the use of a work. If training a model is not allowed under copyright law, it doesn't matter whether or not a work produced by that model is derivative or not (or even if the model produces no works at all)- the training itself is a copyright violation.
In the case of the US fair use doctrine, there is a four factor test which applies[1] one leg of which is the effect of the use on the potential market for the original work. In the example you gave "studying the old masters", it is trivially true that studying an old master has no effect on the future market for those paintings. However I believe copyright holders may well have a stronger argument about the possibly impact of generative AI on the market for their future work because of the ability of people to generate pastiches of their work. Even if those are not deemed to be derivative (which they may or may not be), the use of the original in training could be deemed not to be fair use because it affected the market for the original.
It's nowhere near as cut and dried as people on either side of this debate seem to be making out.
Asking "is it fair use for a [human/computer] to [study/be trained on] copyrighted works" simply does not make sense as a fair use question because the answer has always been "looking at a painting and internalizing it has nothing to do with fair use, of course studying the old masters is permitted." I'm far from convinced the answer should be any different here.
So to me they're barking up a non productive tree by trying to essentially say "the entire model is copyright infringement." Hopefully a judge/jury is not convinced. IMO it should be case by case for any given artifact, whether human or machine produced, does it infringe. Obviously a harder hill to climb for the plaintiffs.