The backup is always made from the instance, so it goes to drives that are visible from that instance. Local might have been a poor choice of words, but it doesn't matter if you are clustered or not. Only those drives/paths that the instance can see are where the backup goes.

It does not matter from where you originate the backup. Meaning that if you can see the ServerX/PathA from your workstation, but the server service account cannot see it, you cannot run a backup to that location.