Honestly even this is questionable. If a running app gets focus between me asking for the new app to launch and that app actually launching, I probably want the existing app that has focus to keep focus until I actively click on the window of the new app.
Once you do that, too fucking late application. Should've been faster, now you don't get focus until I actively do something.
That being said, I've only ever really noticed focus stealing issues happening on Windows or OS X, never Linux.
One-size-fits-all woes I guess.
The network is always down, the disk is always slow, and the OS never schedules your threads. Keep those in mind and your code might be good
That doesn't change the fact that very many apps are in fact that slow that it does matter.
Applications should take about 1s to launch (median for Apple's native apps), including under moderate load, so this problem should never be perceptible. But the fallback behavior you describe is perfectly reasonable.