Will it script?

Speaking of the developer guidelines for Android: the inconsistent behavior of the back button is the single most common irritation I’ve read when it comes to Android. If developers adhere to the new guidelines for Navigation with Back and Up this should mostly not be a problem any longer. A bit puzzling though why the guidelines is consistent in all cases but one: System-to-app navigation. I quote:

If the your app was reached via the system mechanisms of notifications or home screen widgets, Up behaves as described for app-to-app navigation, above.

For the Back key, you should make navigation more predictably by inserting into the task’s back stack the complete upward navigation path to the app’s topmost screen. This way, a user who has forgotten how they entered your app can safely navigate to the app’s topmost screen before exiting it.

Can’t really see why you would want to ruin a consistent behavior like this with special cases. And how would a user be any less confused by ending up at the topmost screen of the app? Other than that, solid recommendations.