It's not that we're "trying really hard" to force sex into a binary. It's that sex in humans *is* binary, because the biology works that way. Other people can use whatever divisions they like, but at some point they'll end up being wrong and/or facing contradiction because they'll collide into the reality of biology. The biologist will be able to predict what will happen, and the person using arbitrary divisions won't.

As I tried to explain, covarying *traits* are unimportant to the fact of sex. We have all sorts of traits (perhaps you mean secondary sex characteristics; "traits" is a vague term.) Sure, that's bimodal. It doesn't mean sex is.

The article you point to is OK, except that it muddles--intentionally?--the topics of DSDs (a far more accurate descriptor than "intersex", which is entirely misleading) and trans people. Trans people, in almost every case, do not have DSDs. People with DSDs do not somehow validate trans people, because they're the outcome of completely different situations.

Biology, and embryology, is enormously complicated: we still don't understand all of the incredible cascade of genes and signalling that take us from fertilisation to sexed foetus. We do know it usually goes right, but sometimes goes wrong. That doesn't imply any intentionality on the part of biology to create a third sex, or an intermediate sex. It's just an imperfection in the process.

But the train only has two destinations. That remains unchanged.