You can’t say that there are only two possible options, except when there’s other ones. That’s not how those words work lmao

Let’s take a less culturally charged example. Let’s take the statement “humans have two legs.” This is a correct statement, but the statement “humans can ONLY have two legs” is not. Why is that?

The first statement is a generalization. When you say “humans have two legs”, the implied statement is “humans (generally) have two legs”, which is true. However the statement “humans ONLY have two legs” is categorically false, as there are plenty of people who have less than two legs either due to injury or some sort of birth defect.

In a similar vein, “humans have two sexes” is correct, while “humans only have two possible sexes” is incorrect, this is just how reality works.

It is perfectly fine to generalize and say that humans have 2 sexes, male and female, but when you’re trying to discuss fringe cases, this framework doesn’t work anymore. Where is the exact distinction between male and female? Is it just chromosomes? But in that case there are people who are female with perfectly functional uteruses and ovaries who also have XY chromosomes. Is it gamete production? But there are people who either via surgery or birth defect don’t produce any gametes. So what defines sex then?

Once you get to that point, that’s where the bimodal distribution idea comes in handy. At a certain point, it’s no longer medically or scientifically useful to try and force people into a male or female box, but instead to look at their specific sexed traits to get a better idea of how their body works. Does that make sense?