> I'm quite sure the entirety of Harry Potter isn't included, but I'm also sure that some of the most popular paragraphs probably are. It's analagous to the kind of stuff people memorize.

No, you are wrong about this. There are good reasons to believe the model memorized the entirety of Harry Potter, as well as Fifty Shades of Grey, inclusive of unremarkable paragraphs, the kind of stuff people will never memorize. Berkeley researchers made a systematic investigation of this. See what I wrote elsewhere.