Unable to access instance that is initially created without a network interface

When creating an instance in the console a user can select "none" for their network interface. This results in an a request that looks like:

{
    "name": "no-network",
    "hostname": "no-network",
    "description": "",
    "memory": 8589934592,
    "ncpus": 2,
    "disks": [
        {
            "type": "create",
            "name": "no-network-jammy-app-server-741cbe",
            "description": "Created as a boot disk for no-network",
            "size": 10737418240,
            "disk_source": {
                "type": "image",
                "image_id": "e50423ec-d67f-4cbb-8cf2-f25903fc44c7"
            }
        }
    ],
    "external_ips": [
        {
            "type": "ephemeral"
        }
    ],
    "start": true,
    "network_interfaces": {
        "type": "none"
    },
    "ssh_public_keys": [
        "fac00a73-ee31-41e6-8a09-a49bc81a6061"
    ]
}

This request will create an instance with no network interfaces, but it will also allocate an ephemeral external ip for the instance. As expected at this point there is no external connectivity for this instance. This leads to a few questions:

• Should this be a valid instance state to request at the API level?
• What is this external ip attached to on instance creation and startup?

After this I stopped the instance, created a new network interface on the instance and restarted the instance, expecting the ephemeral ip to be assigned to that interface. As far as I can tell though the instance still does not have any external connectivity.

I tried looking at the db representation of this, and it looks like the interface is marked as the primary:

root@[fd00:1122:3344:116::3]:32221/omicron> select id, kind, parent_id, ip, is_primary from network_interface where parent_id = 'bece4197-2435-46c7-a861-5775e5830720';
                   id                  |   kind   |              parent_id               |     ip     | is_primary
---------------------------------------+----------+--------------------------------------+------------+-------------
  f294a1ae-5b3a-4759-a8fa-c45082d3f18b | instance | bece4197-2435-46c7-a861-5775e5830720 | 172.30.0.5 |    true
(1 row)

Reproduce the console request with network_interfaces set to none and an ephemeral external IP, then inspect the instance creation and network-interface attachment paths. Compare the API response and the network_interface database state before and after adding an interface and restarting; done should define and implement consistent external-IP behavior for this configuration.