The way people have used it in conversation with me has always meant that they were bisexual WITH an attraction to trans people as well. It is a useful clarification that helps people to know what other people might be open to. Just as "lesbian" and "gay" have specific meanings and have for a very long time, so does "bisexual," so a term that clarifies this additional form of attraction is warranted. We don't want to be harassed and pressured to sleep with trans people, either, for obvious reasons. If someone wants to signal they are open to trans people, it's perfectly fair for them to have their own term. It simplifies and makes safer for all involved the search for prospective mates, just as the other terms do. Lumping in bisexual people with "attracted to trans people" gives trans people the impression they can debate us about who we are attracted to. They can't. Just like they can't debate lesbians and gay men.

If we don't clarify our terms we can't communicate in a way that everyone understands. So no, they are not the same. This should be easy to understand without claiming that someone is trying to declare a fourth sexual orientation. The term pansexual is in wide use already and is used (by those who see themselves as such) for this particular purpose in my experience, so it might as well continue. Splitting hairs about what it should mean is pointless. It works well enough as-is.

Let's stick with understanding the spirit of what this term means rather than trying to invalidate it by forcing it to conform to a taxonomy of sexual orientations. Let them have their term; it gives the rest of us bisexuals a break from harassment.

This isn't hard to grasp. It really isn't.