Comment 5 for bug 1842061

it is expected behavior not a bug.

support for matching on unscoped keys was intentional.
removing it would be an upgrade impact so we would have to deprecate it for a release before we could remove it. currently we discourage using unscoped extra specs in general regardless fo the filter but its still allowed so until we remove that capableity in nova its reasonable for the AggregateInstanceExtraSpecsFilter to be able to match on them.

long term i would prefer if non standard extra specs were required to start with custom:
or another namespace but that is not the case today.

hide_hypervisor_id specifically has been deprecated and should no longer be used.

we introduced hw:hide_hypervisor_id as a replacement to explicitly avoid the conflict with the AggregateInstanceExtraSpecsFilter
https://github.com/openstack/nova/commit/bf488a8630702160021b5848bf6e86fbb8015205