What's the point of "Supported Device Orientation" in iOS application setting?

Question

In XCode4.2 + iOS5 SDK, I set "Supported Device Orientation" to be "Portrait" only. I expect that would make all views in the application to only support "Portrait" orientation. However, while I rotate the iPhone simulator, I found that other orientations still work.

It seems that the method shouldAutorotateToInterfaceOrientation in ViewController is the key to decide whether given orientation is supported. So, why bother to have "Supported Device Orientation" setting in the application level if doesn't limit orientation?

Answer 1

Here's a quote from documentation for UISupportedInterfaceOrientations property:

UISupportedInterfaceOrientations (Array - iOS) specifies the interface orientations your application supports. The system uses this information (along with the current device orientation) to choose the initial orientation in which to launch your application. The value for this key is an array of strings.

E.g. this property determines possible orientations your application may be launched in (it's actually most used on iPad). The latter orientation changes are up to your ViewControllers.