I agree with you, nonny, and I also paused to consider if I knew of any canon endgame f/f where one or both girls is canonically bi. Korrasami came strongly to mind!

There's also this Lithuanian movie, Summer of Sangailė, where the main girl is having a teen sexual awakening and figuring herself out, and she has a fling with a teenage boy, kind of goes "that was nice," then has a passionate relationship with a girl for the rest of the movie.