Comunque ho trovato questo che può essere utile per capire:
The default values for the <supports-screens> attributes differ, depending on the the value of the android:minSdkVersion attribute in the application's manifest, as well as on the value of android:targetSdkVersion, if declared:
- If android:minSdkVersion or android:targetSdkVersion is "4" (Android 1.6) or higher, the default value for everything is "true". If your application uses APIs introduced in Android 1.6 or higher, but does not support specific screen densities and/or screen sizes, you need to explicitly set the appropriate attributes to "false".
- If android:minSdkVersion is declared with a value of "3" (Android 1.5) or lower and a android:targetSdkVersion attribute is not declared with a value of "4" or higher, the default value for all attributes except android:normalScreens is "false". If you are primarily targeting pre-Android 1.6 platforms but also want to support other densities/screen sizes, you need to explicitly set the appropriate attributes to "true".