[steveklabnik]

If it's not a rigorous philosophical work, people will not be very precise with their qualifiers.

For example, in the previous sentence, I said 'people' and not 'most people.' Especially in the social sciences, people assume you're discussing populations, and words like 'most' impede clarity more than aid it.

That said, I don't know the author, and they may be a gender essentialist; they do still exist.