I don't know about in the US but I don't recall the use of em and en dash being taught at school in the UK. We had lessons on the use of comma and semicolon and quotation marks and so on. Dashes seemed like part of the world of literature and journalism, places where typography matters, but not something ordinary people use. Surely this is why dashes are interpreted as signifiers for AI.

I started using dashes about 15 years ago when poorly formatted ebooks made them more visible. Iain Banks is hard to read when every dash becomes a hyphen. The fact that they were (and still are) an issue for ebooks suggests that even people who work in publishing are confused about them.