Copyright isnt a digital moat. Its largely an agreement that the work is available to the public, but the creator has a limited amount of time to exploit it at market.
If you sell an AI model, or access to an AI model, theres usually around 0% of the training data redistributed with the model. You cant decompile it and find the book. As you aren't redistributing the original work copyright is barely relevant.
Imagine suggesting that because you own the design of a hammer, that all works created with the hammer belong to you and cant be sold?
That someone came up with a new method of using books as a tool to create a different work, does not entitle the original book author to a cut of the pie.