Those are the normal tactics used to get a full screen experience. Perhaps your device is preventing it (have you tried on some other devices) or you're not calling the plugin API at the right time? The plugin API is usable only active after the Cordova subsystem has finished initialized, so there can be some delay between the full screen and the first splash screen, especially if you've got some significant amount of initialization happening before the app is ready.
I solved it with editing "SplashScreen.java" file:
I added the Android API Hiding "navigation and status bar" Flags before "splashDialog.show();" function.
But with Crosswalk(19) build: After splash screen hides, they needed to be hidden again.