Which doesn't make much sense, because a bigger dick doesn't make them less feminine...
Case and point, literally every other gal-with-a-cawk in the game.
All it'd really do is make the buttsecksin' dished out less of a "small weak dick in big stronk pucker", and more like "you're pounding their shitpit on equal terms". It alters the tone and, in theory, may change the endings to some specific events/plaps.