Thanks for this post, this is the best explanation for a recurring question in the thread thus farHere, let me try putting it another way.
When we talk about gay men, we don't say that "no fats, no femmes, no Asians" is an inherent part of gay identity because that would be wrong and exclusionary. You can certainly find individual gay men who are not attracted to fat, femme, or Asian men. We discourse over how problematic that is in the community. But you'd never think to define all gay men by "no fats, no femmes, no Asians" because it's a much bigger umbrella than that narrow slice of preference.
Are there individual bisexual people who would only date cis people? Yes. We would never define bisexuality by them. We discuss how problematic the underlying assumptions are towards our trans friends and loved ones. Bisexuality is bigger than that narrow slice so we don't define bisexuality by that slice.