I might not fully grasp what you said, but from my understanding, they were discussing intersex people. In these cases, it's not an either/or situation at birth regarding sex characteristics or chromosomes. It could be a mix of various combinations, or sometimes none at all. The Y chromosome might not be fully present, which means a penis might not exist at birth, or it could be very small (and possibly non-functional for urination), but there may still be internal testicles (which I understand is quite common for some "types" of intersex ppl). In your interpretation, does this mean that there are individuals with a Y chromosome and then there is the rest of the population?

So, we have XY, XYY, XXY versus the others, who might have just one X, two Xs, or a partial Y (I think there were other combinations too). That doesn't seem very binary to me. It's like saying you're either a kid (under 18 in most countries) or an adult, which doesn't cover everyone and doesn't say much either. But maybe we took your comment too serious.

However, labels have always been a tool to simplify life, and they have never been strictly binary. It's similar to organizing a home with labels, there is always at least one drawer labeled other/miscellaneous.

There are as many intersex people as there are redheads, and they can have two sets of sex organs, no organs, or a combination of organs. This wide category range is why the person you responded to mentioned the parts, as these visibly influence how one's sex is documented. Intersex conditions can sometimes make this categorization extremely challenging.