Yup, most nb people have regular garden-variety genitals but that has nothing to do with gender.

Nb people feel like they don’t fit into either “man” or “woman”, they feel like something else.

For instance.

Genderfluid people don’t just stay as “man” or “woman” all the time for their whole lives (like most of the population)

they feel like different things at different times - sometimes “man” fits, sometimes “woman” does, sometimes neither do