This isn't entirely true either. The adjective "binario" has to agree with the gender of what's being talked about, either the grammatical gender of the noun or the natural gender of the person. A salient example could be the noun "piloto". Just as adjectives inflect for gender so do pronouns, so you can say "el piloto" or "la piloto" depending on the natural gender of the person, and inflect adjectives accordingly. Grammatical gender and natural gender are both distict concepts that impact gender inflection in spanish.