> The only thing Fable was given was a clean of copy of the ancient Greek. This is not a bastardization of other translations

FWIW I gave GPT-5.5 two lines of William Cowper's translation (long out of copyright to avoid any filters) without web search and not only was it able to identify it, it was able to continue it verbatim for roughly 30 lines at which point it went off course, but only by skipping like two books ahead. If I had supplied the original text as an anchor it presumably could have kept going.

I didn't try it with Fable because I'm lazy, but all these translations (presumably the ones within copyright too, given the lawsuits) are definitely well known by these models.