It is correct, it is very frequently used in much of the material LLMs were trained on, and the AI is correctly using it, but generally to excess. It uses it so often, that it has unfortunately become a signal that something might be AI written. That is just the reality at this point, and I suspect Em-dash usage by humans will begin to fall off, at least online to avoid that association (until the AI is trained on material that makes it not use em-dashes, at least).