Bisexuality is a specific orientation, it is.
I’ve not only posted aspects about it, you yourself talked about it.
That’s exactly what bi erasure is.
Except when some people in the LGBT community aren’t cool with them, as you have noted. In the a similar way trans people get hate from TERFs trying to exclude them.
Because those are different terms. In the same way someone wouldn’t refer to a homosexual man a lesbian. And why you would call a bisexual person bisexual.