I have to disagree that any of the human kids were written with "ambiguous ethnicity". They were clearly coded as white, and betaverse Bro was explicitly white before Hussie retconned it in response to POC fans demonstrating that his ~aracial~ claim was bullshit.

I'm also a bit puzzled that you interpret the linked post as saying "m/m's popularity is purely a result of misogyny". It provided the pairing stats from AO3 -- and certainly didn't "act like het is this poor oppressed minority", considering that the extreme underrepresentation of f/f was one of the things it showed.