One of the downsides of using an expert LLM to write for you is that they know all that perfectly well, even if you don't, and aren't too bothered by such a chunk. It's like reading any Wikipedia article on mathematics... This is the kind of thing that people are documenting in the LLM-user literature in creating an illusion of expertise (or 'illusion of transparency'). Because the LLM explains it so fluently, you feel like you understand, even though you don't. Hence new phrases like 'cognitive debt' to try to deal with it.

(This is also why people like cramming or lectures rather than quizzing or spaced repetition, because they produce a certain 'illusion of depth' https://gwern.net/doc/psychology/cognitive-bias/illusion-of-... ).