I'm confused by why existential biorisk seems to not exist as a term.

The context here is that I've now talked to around a dozen people working in (or seriously considering working in) the field/cause area of global catastrophic biological risk (GCBR). Some of these folks are longtermist and/or x-risk oriented, and seem to care exclusively about the tail end of GCBRs (i.e., the part of the GCBR distribution that might lie in existential territory). Others aren't so focused on tail/existential risks. To me, lumping these two together under the single banner of GCBR leads to a degree of confusion and talking past one another. Anecdotally, I've witnessed a discussion on GCBR research directions where half an hour went by before those involved realised the source of their disagreement was x-risk focus, or lack thereof.

(I've heard the argument, in response to my "existential biorisk" terminology proposal, that all GCBR work is useful for reducing x-risk, and that this is why the distinction I point to is not made. While I do agree that some or even all non-x-risk focused GCBR work could turn out useful for reducing x-risk, it'd be a suspicious convergence if the current portfolio of GCBR work is optimal for reducing bio-related x-risk.)

Which brings me back to my question: why is "existential biorisk," or a similar term, not in use?