and a majority of them do not consider themselves trans

And in my experience it's the opposite. But either way we are going in to anecdotal territory which isn't helpful. What's important that we agree on is that non binary folk absolutely have the right to decide for themselves either way.

Concerns about erasure is valid, but the language matters as not to be exclusionary. There is value in saying NB, intersex and fluid are distinct identities, but not in saying they are mutually exclusive from or inherently "not trans".