I feel you. I've been using en-dash in my writing for decades, but finding myself removing them now for fear of being mistaken for an LLM. (They tend to use em-dash, but I don't think people are going to distinguish between – and —.)
Why wouldn't they. Never studied them. Never even thought twice about the dashes in a sentence. Didn't realize they were different till like a few months ago when everybody suddenly started focusing on how "AI" it makes everything look
I would think to most people, (myself included!), it's just a 'dash'. A sentence was written with a dash - you could just ingest and read past it, like a comma.
Not saying this is accurate usage, maybe just real world usage.
I would hope most people can distinguish between the really short dash and the longer forms, even if they don't know any of the rules around them. But n versus m I don't expect people to notice.
And of course, the reason that ChatGPT sounds like that is that it's what a whole lot of explanatory expert blog posts did, and so when ChatGPT is told to talk like that, that's what it does.