I's not IMHO so simple: If you don't "look the part" then of course you are noteworthy. For example a child from korean Immigrants that's born in (ok, let's use) Germany may feel like a German (and is a German!) and maybe didnt't have any connection to "Korean Culture". Not only racists will...
Or maybe it's sounds odd and clinical, like "species" sounded odd and clinical - and not like fantasy but science fiction - some years ago when it replaced (as the correct term) the established fantasy term "race".
Do you maybe mean a different book?
"The lore of humans depicts orcs as rapacious fiends, intent on coupling with other humanoids to spread their
seed far and wide. In truth, orcs mate with non-orcs only when they think such a match will strengthen the tribe. When orcs encounter human who match...
As Addendum to the previous post about the "Dragonmarks article on the old WotC website": Two "kanon" continuationions of the article from the author:
IFAQ: Moons and Lycanthropes
Dragonmarks: Lycanthropes
The mechanics (crunch) are IMHO the priority because it's the only hard fact the authors can control. The flavour (fluff) (description, culture, relations to other species etc.) is something that (sometimes) varies between the settings - so for example the standard Players Handbook halflings...
No. They can represent biracial people for someone (and I made the error in a former post to not consider this - sorry for that 😔) - but saying "these creatures don’t exist, so they represent real things" is IMHO way to simplistic: So elves are simply beautiful humans, dwarfs are stocky humans...
Khoravar:
Now included as a unique playable species in the world of Eberron
And it's one of my pet peeves but Half-Elves and Half-Orc were never biracial, they were (and are) hybrids because Elves, Humans and Orcs are different species.
The name "Khoravar" for the distinct Half-Elven "race" of Eberron was established more than twenty years ago, so they didn't "came back with a name that doesn't normalize being biracial".
IMHO it's in the Name: Khoravar means "Children of Khorvair", Jhor'guntaal means "The Children of Two Bloods" Khoravar are (purposely) distinct from the humans and the elves this race orginated from, the Jhor'guntaal are "the best of the two" and live within the culture of their parents.
AFAIK the Khoravar are a truebreeding race (species?), the Jhor'guntaal are not.
A "system for species mechanics for mixed ancestry characters" is IMHO a not so great idea, because I'm pretty sure it would be a "mix and match"-system: a dream for the min-maxing players and a possible nuisance...
And that's the reason why nobody knows a guy called Shakespeare anymore and the people stopped hundred years ago playing his plays or making movie version of his plays or enact interpretations in other medias - or using motivs from his plays in their work
It's totally based on a animal, the drumroll harvestman.
If if we would follow your logic then a dog is only a furry human, a cat is also a furry human - but with a high dextery modifier - and a spider is a human with eight arms.