NativeWidgetMus currently does not implement the methods that support native theming of the frame
  - ShouldUseNativeFrame
  - ShouldWindowContentsBeTransparent
  - FrameTypeChanged
  - IsTranslucentWindowOpacitySupported

In mus the client can already decide to render what it wants in the non-client area. The only possible override we would want is for the immersive mode light-bar. However our maximized mode support has not been implemented yet.