The Subscription profile says:

PAO Subscription Resource Profile The subscription resource should accompany the initial message bundle to provide a mechanism of informing the ordering provider when there is a change in the order as indicated by a change in the Task resorurce. The subscriber has the option of receiving a notifiction when a change occurs or receiving the updated task and any relevant order resources (device, service, medication)

But the flow diagrams in the background material don't seem to include the option of receiving the updated task and related resources. If that is an option, that should be part of the flow diagrams (or at least addressed in the background narrative.

As well, the narrative has a few typos:

The subscription resource should accompany the initial message bundle to provide a mechanism of informing the ordering provider when there is a change in the order as indicated by a change in the Task resource. The subscriber has the option of receiving a notification when a change occurs or receiving the updated task and any relevant order resources (device, service, medication)