That very much depends on the topic being studied. I've passed plenty of exams of different levels (school, university, professional qualifications) just by reading the textbook and memorising key facts. I'd agree with you if we are talking about something like maths.

Also, there's a huge difference between passively watching a teacher write an explanation on a board, and interactively quizzing the teacher (or in this case, LLM) in order to gain a deeper and personalised understanding.

The issue is verifying the LLM is returning actual facts. By the time you’ve done that consulting sufficient reliable information, you don’t need the LLM.