The article seems to be arguing that applications shouldn't keep resources or keep running when not visible without making it clear to the user and providing a

The article seems to be arguing that applications shouldn't keep resources or keep running when not visible without making it clear to the user and providing a convenient way to make the app release its resources and completely stop running. The author is saying that most apps don't really need to keep doing things and using resources when not actively in use and visible(with GPS navigation and music players as two examples of apps that do); if an app doesn't need to keep using resources while not visible, it shouldn't need an explicit exit button because it should be releasing all of its resources when you leave the application with the back button.