Many people recognize that gender—how a person identifies, presents themselves and is perceived—has nuances. Some people identify and present as women, others as men, and still others as nonbinary.
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My understanding of it is there are two “typical” sex genotypes, but the expression of or development of various sexual traits, and traits culturally associated with either sex, makes these typical examples the uncommon ones. On top of that are the classical examples of genetic Intersex.
Even things as simple as finger lengths: males are more likely to have fingers which are all a different length than each other, but high testosterone presence during natal development and early childhood can bring this characteristic out in females. In recent years an olympics committee disqualified multiple assumedly typical women for having a higher testosterone than their established limit, despite it being the same as their relative baseline.
