Things like books are proof that actual humans use em dashes, that wasn't ever the contention.

What's needed is a writing comparison before/after 2022 for these users. If there's a sudden 200% increase in the use of em-dashes from one month to the next, it's a very strong indicator that the user started LLMing their posts.

Perhaps I should have qualified that humans use them in casual writing, website comments and the like, and not just in formal, published works that probably had an editor.