NGL the idea of "choosing" what race you are is something that lots of mixed race people have issues with, and I really regret Tolkien didn't put this racial binary into his half-elven characters because the fantasy genre has had to carry some Silmarillion One Drop Rule henceforth.
Obama is black and white. Obama did not have to choose to be black or white and gain the powers of bass guitar or country club membership. Race, being an ultimately social construct, a noumenon with no physical basis in the observable universe, is logically inclusive. If it makes no sense to ask someone if they are black xor white, then the same goes for a half-elf being human xor elf.
I'm unsure why this is a reply to me. Are you arguing against the "Children of Different Humanoid Kinds" sidebar in the 2022 "Character Origins" UA by comparing it to the absolutely abhorrent Jim and Jane Crow era "one-drop rule" racial classification legal principal of most of the first two-thirds of 20th-century United States? If so, I think discussion of such is against board rules, and I didn't say anything about the UA rule, of which I'm not in favor.
Professor Tolkien, on the other hand, wrote about a world in which the souls of men and elves, while housed in biologically similar bodies, had separate fates because, in that world, men and elves are separate acts of creation. The conception of a baby of both human and elvish parentage doesn't create a third fate, but a dispensation is given in which certain such individuals are given the choice of which fate they and possibly their descendants will be subject. Importantly, the making of this choice doesn't cause an individual to cease to be "Half-elven". Elrond, who chose to be counted among elves, continued to be known as Elrond Half-elven. The descendants of Elrond's twin brother, Elros, although he chose to be counted among men, were included by Tolkien in "the Half-elven" all the way down through Aragorn and his descendants, even though they no longer used the title and were widely regarded and themselves identified as men. So the "racial binary", as you call it, persists within the Half-elven characters and, as I pointed out up-thread, can be seen in Aragorn's positioning between Arwen and Eowyn in a love triangle. His choice between them, although made "off-screen", like the choice of the Half-elven made by other characters, is exactly the trope of being torn between two worlds. Or is the problem, as you see it, that it's being resolved dramatically? I think, if you have a character that's torn between two worlds, then the dramatic question arises naturally "which one will you choose?" and the resolution of the drama will involve answering that question.