I was often wondering if this was the case, because it didn't make sense to exclude trans men and women from a bisexual's sex pool. They are not separate sexes, since they attempt to conform to either male or female ideals and portrayals. And while intersex is physically mixed in sex characteristics (hormones, body type, genitals and sexual organs), the vast majority of them tend to accept themselves as male or female. And, as you said, while nonbinary is a nonconformity to gender roles and presentation — in however way they wish — they still sport physical aspects that determine their underlying sex. Not that anybody needs to know what it is — as I say, if you're not sleeping with them or treating them as a doctor, you don't really need to know what lies between their legs.
In my experience, I've never slept with a trans man before, so I can't say for certain that I like trans men. I can say, though, that I've seen a few in my time and even I can't say no so easily. This shows that I am, indeed, attracted to trans men as well as cis men. In saying that, I may have an issue with certain genitalia since much of my sexual pleasure arises from giving oral. And I always like to play with theirs.
To be honest, the whole discrepancy between bisexuality and pansexuality makes me wonder how we'll ever reach strong acceptance from the cis-het community. Yes, we need to have discussions about this with our wider communities to help them come to our table. To understand. But it's kind of hard when there's so many in the queer community striving to be different from everyone else. So different that it borders on confusing.
And if some of us queer people still can't understand wholly about the other letters in the rainbow alphabet, how do we expect those outside the LGBTQIA community to learn?
I wish we could just say that some people are sexually attracted to certain (or all) people and that's okay, and that some people do not conform to their assigned sex at birth or the gender roles of society, and that that's okay as well. AND that everyone approaches sex and love in their own individual way. But it seems that it is more than that — whether you're a bigot or a queer person.