How does the monitoring system handle diversions?
In all Available Plans, the system follows all detours without exception.
So if you redirect website "example1.com" to "example2.com" and your event setting is on "example1.com", the system will report the status from the endpoint "example2.com".
This saves you from having to edit monitoring events once they have been created. Ideally, however, you should change the monitoring event directly to the new endpoint "example2.com".