DefaultRequestQueueNotificationRule

The default: units freed on a resource go to the waiting request that entered its queue first, across every queue that may hold a request for the resource, whether the request names the resource or a pool the resource belongs to. Each queue still offers its requests in its own discipline.

The resource applies this order itself, request by request, which an order of queues cannot express. Its iterator, for anyone who calls it directly, gives the queues in the order they were registered.