With all due respect, sex is not a spectrum.
It's a clearly a binary. Yes, there are many exceptions and edge cases, but they are all based around a universal binary biological structure.
You don't have say three distinct sexes required for reproduction outside of sci-fi. It is a binary with some edge cases and variations in how exactly the two parts of the binary interact.
It's far closer to a binary distribution than a bi-modal distribution. You can be pedantic, but that's not a real arguement. I admitted there are edge cases.
This is not tied to pure outcomes and is derived from actual earth bio-chemistry.
There is no triple helix or quadruple helix as a foundational system of genetic bio-chemical reproduction.
When you flip a coin, there is a chance that it will land on the side, yet we still use a coin flip for a 50:50 probability scenario because it is close enough.