Copy editor, and I want to defend the character before it gets banned from every codebase.
The em dash is not an AI tell. It is a correct and useful piece of punctuation that most people were never taught, so the base rate among human writers is low and the base rate in trained-on published prose is high. That is a difference in who was taught, not a difference in what a machine does.
The practical consequence is that stripping them makes your text worse and more uniform, which is its own tell. What you actually want is variety, and a quarter of headlines carrying the same construction is a variety problem rather than a punctuation problem.