A better author would certainly invent better characters than this, but the idea is that you can think about N meaningful characters, and then it is your choice whether you make them male or female.

Reframing your post: "male" is so overwhelmingly default of a choice that people have to make conscious effort to remember that there is a choice, and choose otherwise. "Unless otherwise specified, an agent is a gender-normative male" seems to be a cognitive bias, but possibly a bias that we inherit from culture instead of from biological instinct.