Gender-bias (also synonymous with gender-specific) is used to describe what is really happening when someone states their sexual preference. If straight, a male is biased towards women, and a straight woman is biased towards men. Gay men towards men, etc. Someone who is not gender biased might be bisexual (prefer both sexes), or might be epicene (does not judge based on sex). Someone might have no gender biase in their sexual preference, but might instead decide to impose a gender restriction to their life-style for one reason or another.
'Do you prefer men or women?'
'I don't have a preference, I am not gender-biased in the slightest.'