rockot@ points out:
"""
I think maybe the issue here is that the word "handle" is a bit of a
misnomer at this point, and it's setting the wrong expectations for what
the type should represent. Keeping track of a shared buffer reference in a
way that can be used consistently and reliably across process boundaries
requires more than just a system object handle, in practice.

Imagine we renamed it to MappableSharedBufferReference or something, but
then imagine that such a rename would create more churn than is worthwhile.
"""

Giant refactors are never fun, and are best done at odd hours of the day.