AI crawling has come into the spotlight more and more, and I think with the Actor's/Writer's Union strikes we're slowly moving the zeitgeist away from killer HAL5000s and toward AI companies stealing and profiting off the intellectual works of authors.
Without a doubt the pirated material is a problem, however would it be more practical if the company had purchaused a copy of the library and fed it in? Fan-made derivatives are essentially people reading the novels and creating their own extensions. Even if you had it remove all the copywritten material, a robot is essentially using the same logic. Writting a basic story is formulaic, especially when it doesnt have to be standout. Netflix is a great example of stamped-out material. Not bad, not great - very predictable and formulaic in its design.
Part of 'art' is that it belongs to the public once it is made public. Whatever the author's original intentions were, it's now something the everyone to interpret.
And aside from that the large companies getting into ai generate so much money that whatever they settle for is a drop in the bucket, especially if they can go on and use this material.
I think it's a bit different when you're taking someone else's thing and then reproducing it in some fashion for commercial intents. E.g. some companies don't mind if you make fanfics, mods or art of their IP just as long as you don't try commercialise it. GW in this regard is inconsistent, because they're happy with people making fanfics, models & fanart of 40k but not unlicensed animations or games.
What is the issue here is not about whether they pirated or legally purchased the books they fed into the AI though. What matters is that they're producing a commercial product using GW IP without any commercial license. A similar comparison can be made to how movies using book sources, TV shows making parodies, DJs making remixes can all substantially alter the original source in totally transformative ways and yet still fall afoul of copyright issues unless they get a proper license agreement with the rights holders.
Copyright law is its own mess of nonsense, what with copyright favouring the rights holders over the rights of the creators to the ludicrous extent that companies will keep defending their claim to the author's work for the author's so called benefit long after the author has died... But that's another issue entirely.
Really though I am just hype for lawyerbowl between extremely litigious, extremely greedy companies. If they really go at it it'll be a scenario where whether the demon or the monster bleeds, the public wins