I have --- set to autocorrect to —. I've been using it in formal writing for 30 years. When we were in high school, we had a "Dash Party" in English class, where we ate Twinkies and learned about the different dashes.

I would argue that LLMs overuse the emdash more because they overuse specific rhetorical devices, e.g. antithesis, than because they are being too correct about punctuation.