So, if I'm understanding right, it is using the database server instances as the current Aurora does. You just aren't responsible for managing them, the service makes those decisions within the spectrum of Aurora's capabilities and can change it in a very small time increment.
EDIT: pretty impressive though, looking at James Hamilton's criteria for "Automatic Management and Provisioning" here: https://www.usenix.org/legacy/event/lisa07/tech/full_papers/... , I think this addresses everything database related, as long as you are under the maximum capacity of Aurora.
Aurora already spreads each "10GB chunk of your database volume is replicated six ways, across three Availability Zones." It looks like from the diagram they are taking advantage of that fact and spinning down the instances that serve off those "disks"
EDIT: pretty impressive though, looking at James Hamilton's criteria for "Automatic Management and Provisioning" here: https://www.usenix.org/legacy/event/lisa07/tech/full_papers/... , I think this addresses everything database related, as long as you are under the maximum capacity of Aurora.