No, sexual fluidity isn't a sexuality in itself. It's quite different to the bi-cycle or similar. See Dr Lisa Diamond's research on the topic.
For example, there's quite a big difference between someone who was always bi expressing their attraction to women for half their life then later their attraction to men, and someone who was heterosexual becoming gay at 40.
For example, there's quite a big difference between someone who was always bi expressing their attraction to women for half their life then later their attraction to men, and someone who was heterosexual becoming gay at 40.