OK so let us clear up some misnomers about registrations. When a REGISTER occurs it takes the Contact URI and stores it in a User Location memory. Then the PBX will try to qualify that location based on the Qualify settings. The PBX will keep that location in memory until the Expiry timer is hit or it cannot get replies from the qualify after X attempts.
This is not a real-time active showing. The device could loss connectivity and until it either expires or the PBX considers it a time out, the PBX will show it REGISTERED. So right there this is a false flag because the device is obviously down, it has no connectivity.
So at this point, it doesn’t matter if it’s a Peer or a registered Location. The PBX will attempt to qualify it (as long as that is turned on) and will make it unavailable once it can’t. Or it will drop it when it expires.
This is no way to indicate if the device is 100% up or not since the device can have an Expiry time of an hour and it would take the PBX about 2-3 minutes to consider it dead when qualifying it because it lost connectivity.