@lutostag The order is implicit in those cases indeed. Whenever a channel is closed, either because it never got anything released on it or because it was explicitly closed afterwards via snapcraft close, installs and refreshes will fallback to the channel that would offer less risk, potentially jumping through multiple channels.
The order is the one implied in the command output:
- edge → beta → candidate → stable
The arrow pointing upwards in the info output hints at that behavior.
There are other details surrounding channel terminology in the documentation.