That kind of fits with Altman saying they put them in because users liked them (https://www.linkedin.com/posts/curtwoodward_chatgpt-em-dash-...)

I guess in the past if you'd shown me a passage with em dashes I'd say it looks good because I associate it with the New Yorker and Economist, both of which I read. Now I'd be a bit more meh due to LLMs.