Using Oracle 12c database (SCAN) with Oracle 8 client
Oracle will try to have at least one active scan listener on every node of the cluster. They are running on a vip and that vip can be relocated to any of the nodes.
As long as your app does not care in what instance it connects, it does not matter where your connection takes you. Problem comes when your app tries to connect to a specific service that is not on the node where the first returned listener address is located. In that case you are better off with a regular address list.
The scan address is unavailable during maintenance and while it is reassigned.