Let’s say you’re controlling a piece of machinery with an app in the background and the machine starts on fire. Wouldn’t it make sense for the app to steal focus so it can show you some alarms (in addition to audible alarms which you may not hear because they’re in another room).
Having actually worked with industrial machinery, the proper UI for this is 1) unimpeded view of machine and 2) big red physical emergency stop button.
If you're relying on focus stealing or popups or notifications to tell you when your equipment is on fire, you're doing it wrong.
Also, the presumption that I'm going to wait around for 5+ seconds whilst an opens is unrealistic.