I used to be a pretty active gender critical feminist, who has now given up on them, and even I can't recall much that could be considered biphobia. Feminism has a lot of inherent problems, but the ones causing them are usually snotty upperclass straight women who demand blind obedience from other women.

In feminist circles lesbians are sort of shunted aside and bisexual women are completely ignored. On the other hand, in gay spaces where feminist lesbians dominate, hatred of bisexual women is palpable. Those spaces are few and far between, thank God.