I have other questions. Is the observation period triggered when a business user triggers the key user action in a session, and that will trigger an alert 5 minutes later? - Have you set any custom alert profile to delay the alerts. This will be true only if the users initiate the action, but will alerts will be generated as per the average/ median time response.
Or is the observation period only triggered when the average/median visually complete time is longer than 5 seconds? - Above comment should answer it.