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.
I’m not sure I’m representative of “most people” in this respect (I have always used both n and m dashes), but I personally find the difference between n and m dashes bigger and more noticeable than the difference between regular and n dashes.