This, Harry potter is a terrible example, even weak models know the rough story of Harry Potter unprompted.

If you want a real test, go test it on some Japanese light novel, or some harry potter fanfiction, and see if the model actually understands the plot details.

For reference, Opus/GPT-4 know the rough story of moderately popular light novels/mangas without any context given. They however do not precisely understand the fine-grained details of the story, like which character will win in a fight.