Yeah, but it's non-fiction, which means that coherency does not need to be maintained during generation - it can always be recalled from a) the model's training (assuming this event was in the training data), and b) any context it was given in an initial prompt.
The test here was, specifically, coherency, which I feel is going to be difficult for even SOTA models to track over the standard novel length of 100k words (80k for YA novels).
Maybe if it's a novel about a single individual in a limited setting (so, pretty boring, but we are not measuring quality of plot), a SOTA model can keep it coherent?
I dunno how it would do with something like Stephen King's IT or Under the Dome (multiple parallel plots over 450k words, involving multiple main characters, with events on every single page needing to be coherent with the rest of the book), but before we even get there, standard novel lengths (around 100k words) would be the test for coherency.