[EnergyAmy]

You and the other person are probably talking past each other. For most people, "gender" is merely the polite way of saying "sex", and that's probably what the other commenter was referring to.

Gender in the sense of "the social roles and norms on top of biological sex" is indeed a construct, though heavily informed by the biology that they're based on. Biological sex is very much real and not a construct.

[defrost]

Of course biological sex is real and strongly bimodal with outliers, who ever said otherwise?

[EnergyAmy]

Technically correct, but to be specific sex is binary, not merely bimodal. Sex is entirely defined by gametes, and is binary in anisogamous species such as humans. Isogamous species don't have sexes, they have mating types (and often many thousands of them).

There's actually an ideological movement to try to redefine sex based on sex traits instead of gametes, but this ends up being incoherent and useless for the field of biology. Biologists have had to publish papers explaining the fundamentals of their field to counter the ideological narrative:

Why There Are Exactly Two Sexes

https://link.springer.com/article/10.1007/s10508-025-03348-3

That's why I thought it was worth mentioning. Many people are confused because of the culture wars. To bring it back around to the general topic of this thread, it's fine to store someone's sex as a boolean, because sex is binary and immutable. Storing cultural constructs like gender as anything other than an arbitrary string is asking for trouble, though.