To keep things simple, any change should have a notification. If not, you can be sure someone would be here complaining.
Swiss customer service told me that the robot should send out an update email even if the change in departure time is only 5 minutes.
The change was received by Swiss and the automated system failed. This has been confirmed to my by the agent.
I should have received the update more than a month ago
This is a pathetic situation that needs to be remedied