The baborc plant has a gender. Orc ashes act like seeds. But in life, in terms of understanding human romantic interaction, they don't- it was more a shorthand for explaining why orcs have no interest in romance because many IF readers look for that type of thing.
In essence, we can say those orcs (in this world) are both male and female, like many, not all, plants- but have the appearance of muscled males, the stereotypical 'barbarian.' This is what I find most fun about orcs.
Also, this game is set in a medieval-esque world. Folks here are not overly concerned with deep discussions about gender. But I take your point- many do wish to gender their MC.
-On a side note, the follow-up does allow you to pick your gender.