Paul L on Nostr: As far as I can tell because you see the presence of the physical NIC in virsh or ...

As far as I can tell because you see the presence of the physical NIC in virsh or virt-manager you have made a conceptual jump that Libvirt is taking any responsibility for the physical NIC and that's just not in scope.

If you have made a bridged network in Libvirt that includes a physical NIC, all it does is makes the physical NIC a member interface of a bridge.
It still does not get involved in how IP addresses get assigned to the physical host for itself or downstream.