OK, but please don't do what pg did a year or so ago and dismiss anyone who wrote "delve" as AI writing. I've been using "delve" in speech for 15+ years. It's just a question where and how one learns their English.
That's what makes it such a good giveaway. I'm happy to be told that I'm wrong, and that you do actually use the proper double long dash in your writing, but I'm guessing that you actually use the human slang for an emdash, which is visually different and easily sets your writing apart as not AI writing!
"the formal emdash"?
> AIs are very consistent about using the proper emdash—a double long dash with no spaces around it
Setting an em-dash closed is separate from whether you using an em-dash (and an em-dash is exactly what it says, a dash that is the width of the em-width of the font; "double long" is fine, I guess, if you consider the en-dash "single long", but not if, as you seem to be, you take the standard width as that of the ASCII hyphen-minus, which is usually considerably narrower than en width in a proportional font.)
But, yes, most people who intentionally use em-dashes are doing so because they care about detail enough that they are also going to set them closed, at least in the uses where that is standards. (There are uses where it is conventional to set them half-closed, but that's not important here.)
> whereas humans almost always tend to use a slang version - a single dash with spaces around it.
That's not an em-dash (and its not even an approximation of one, using a hyphen-minus set open—possibly doubled—is an approximation of the typographic convention of using an en-dash set open – different style guides prefer that for certain uses for which other guides prefer an em-dash set closed.) But I disagree with your claim that "most humans" who describe themselves as using em-dashes instead are actually just approximating the use of en-dashes set open with the easier-to-type hyphen-minus.