Yes, several of the most popular (and even lesser-popular but newly open-sourced models such as Gemma 3 27b) overuse Em dashes. Even when prompting them to not use dashes, they almost can't help themselves and include them occasionally anyways as it must be part of their learned stylometry. It's just not a common symbol to use at all as most people generally use commas for the same purpose. I can't even remember learning about Em dashes in my college english classes.