We're not talking about humans vs LLMs in general, we're talking about humans copy-pasting LLM output as if they wrote it themselves. It's less "LLMs are bad" and more "if you want to communicate something specific to me, LLMs are a bad substitute for your own writing".
Oh I see I’ve misunderstood. Your analogy is restricting the scenario to no interaction with LLMs. In that case, there are still some reasons LLM writing might be prefereable for students: for non-native speakers, and for math teachers new to match developing a new curriculum (sucks, I guess, but it certainly happens), just to name a couple.
One question to ask is why is your contrived LLM scenario any different than a math teacher using a textbook, or district/state worksheets? Math teachers typically do not write the course text or exercises, and never have. Very few math teachers do their own writing.
