The false positive rate for assuming em-dashers are AI is probably very low right now. I doubt whatever you write is valuable enough to justify the extra time and mental effort of figuring out if something is AI or not.

Internet slang like "lol" came from trying to text on those shitty number pads on old cellphones. I expect similar slang will come about in the future from humans trying to prove they're not a dirty clanker. Sacrificing the em-dash is just the beginning of this. Soon, we're all going to be typing without rhythm.