I agree that it would be nice, for example to display effects only on the feet of the woman and not the feet of the guy. However it can be difficult to determine the gender of a person with the current AI models, especially if the person is half visible, and considering that there are femboy/futa.
I guess it cost nothing to always detect a gender on all body part, it can be useful and the user would just select both genders to revert to the current operating mode.