Did the original owners of the books no longer have them in their possession afterwards?
Theft involves removing from the source, Copyright violation is distributing copies without a legal right to do so. Training is fair use.
The judge found that it constituted copyright violation. Purchasing the books would cover their responsibilities with regards to training. The claim that they are destroying books to hold copyright is incorrect. The judge cited precedent that said instances of not destroying the originals were also fair use, his claim about destruction was to say even if this precedent were not considered fair use, the destruction that was already occurring (because it is easier to scan loose pages), invalidated one of the arguments against it.
The ruling was on training took the form
If A is ok then B is ok, but even if A were not ok, B might still be ok.
Excellent. I will thus take a copy of the latest Disney movie and train myself on it while claiming fair use as a defence to the accusation of copyright infringement.
You can do that legally as long as you do not confuse people that what you create might be an actual Disney product, or that you try to represent it as actually created by Disney.
Both of those are protected by law. Learning from a Disney movie and creating your own thing is not, and should not be, disallowed.
What law in what country?