Revealing true sex to be so ridiculous regarding intersex people, it is simple to see how ridiculous it is for non-intersex people as well. The only difference is that regarding non-intersex people we are quicker to assume their sex. With intersex people existing, none of us are safe from the hard questions they prompt.

If you are cisgender and non-intersex, you have never asked yourself "how do I know am a female/male." Everyone tells you so, your body looks like other females/males, and no one challenges you. Until now. Consider that intersex people go through the same process. It's not until an unexpected medical issue prompts for a test and reveals a surprise. A friend of mine has frequented hospitals his entire life and only by age 21 was his intersex condition (CAH) discovered.

Consider mosaicism. Intersex mosaicism can easily be undetected because it may never cause a problem that prompts investigation. Yes, you could have trillions of cells of the "opposite" sex in your body and never know. Even a test can give false negatives. If you have 1 trillion opposite sex cells, it would take 50 karyotype tests (statistically) before yielding the correct result.  Perhaps I am personally made of half female cells (simply non-gonadal cells). Each of us is potentially intersex.

Josef Kirchner once worked with Jerry Leach before supporting transgenderism and learning he had intersex Mosaicism. He makes a great insight.

Given the persisting female artifacts like nipples and the raphe, every male is intersex. Even more convincing is that every person has both female and male hormones. Women may find testosterone disgusting, but she has it. Men may think estrogen is weakening (I know someone who refused soy thinking it was linked to estrogen) but it flows through and affects their bodies too.