iOS [UITabBarController shouldAutorotateToInterfaceOrientation]

If you want to change the UITabBarController's view orientation according to device's orientation, most of time, it's suggested that you should create a subclass of UITabBarController and override the method shouldAutorotateToInterfaceOrientation. today I found that if all of the children view controllers in UITabBarController support the same orientation, then you don't need subclass UITabBarController. that means all of view controllers' shouldAutorotateToInterfaceOrientation method should return the same value for each orientation. I don't why. and didn't find any document.