This is an absolutely absurd accusation, I have used em-dashes CONSTANTLY in my writing LONG before AI was a thing.

I don't even know how the hell to address the claims about pacing or spacing (????? the spacing/formatting is the same as it has always been). Please think for two seconds before making insane claims like this.
I hope you don't get bothered by people wildslinging AI accusations :'). Goshhh imagine pouring your heart out to your work and then getting accused by people who don't have the capacity to assess AI-use and rely on lazy generalizations such as em-dash usage.
Like, even if AI uses em-dashes, there is no intentionality to it compared to an actual human making writing decisions.
Something I personally notice in AI generated stuff is that they overuse it and usually use em-dashes even when a colon, comma, or semi-colon would make a better fit to the sentence structure
I appreciate it, and don't worry, I don't take it to heart!! It's just a very serious accusation to make when it's so easily disproven in my case, I'm baffled what this person was thinking. And I have heard AI tends to overuse/misuse em-dashes like you said, I mean it was trained on human writing that uses em-dashes in the first place after all 😭