This issue, as I understand it, is about the actual choice to use an emdash character (—) rather than a hyphen (-), and about the effort involved in doing so. It's not about sentence structure.

I don't really understand how AI developed a bias towards doing it correctly rather than doing it the lazy way. But hearing so much about emdashes qua LLM detection mechanism eventually just got me to decide that typing an ordinary hyphen really is just lazy. And then I ended up configuring my system to make it reasonably easy to type them.