I notice you go on to provide an argument only for why it might not be true.
Also, seeing the other post on this, I asked chatgpt-4 for a summary of “ The Ruby of Kishmoor” as well, and it provided one to me, though I had to ask twice. I don’t know anything about that book, so I can’t tell if its summary is accurate, but so much for your test.
It seems pretty naive to me to just kind of assume chatgpt must be respecting copyright, and hasn’t scanned copyrighted material without obtaining authorization. Perhaps discovery will settle it, though. Logs of what they scanned should exist. (IMO, a better argument is that this is fair use.)