> The reason for this "fad" is straightforward — there are a lot of middle-aged humans who are undiagnosed because ADHD was effectively "not a thing" when GenX were kids.

Or to the extent that it was, they only knew of it through narrow or outright inaccurate stereotypes. It's become a somewhat common story over the past few years in online ADHD communities for Gen X and older Millennial parents to get their kid diagnosed and have a "wait, that's not normal?" reaction to the explanation of how the condition actually tends to manifest.