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.