attractivness attractivness system Like / Dislike sexes

[Ishallbe]

I need to understand something that I can't find an explantion for. If a sim for example a female sim, likes male sex, but dislikes female sex, that means she is straight. but what would it mean if she didn't disliked female sex, or rather she'd only like male sex, would that make her a bit bisexual? does it mean she will like men more but will be O.K with female sex as she does not dislikes it?
See that's what I thought it would mean, but appearntly she still counts as straight as my other female sim is not compatible with her oriantion...
If in both scenerios this sim is straight, then what's the point in having the dislike sex option?