Okay! Taking this over to the asexual thread. (And really I should get back to writing instead of posting here, bad me.)
Again no.
While some bi people are only attracted to two genders, this also isn’t necessarily the case.
Hrm here’s one tumblr post, which wasn’t the one I was looking for.
http://anagnori.tumblr.com/post/82602534445/is-it-wrong-to-label-oneself-as-both-bi-and