"Using Viewports" tutorial incorrect when SubViewport shares parent World3D

https://docs.godotengine.org/en/4.1/tutorials/rendering/viewports.html reads:

> - Node3D
> - CameraA
> - MeshA
> - SubViewport
> - MeshB
> - CameraB
>
> `CameraA` will display on the Root [Viewport](https://docs.godotengine.org/en/4.1/classes/class_viewport.html#class-viewport) and it will draw `MeshA`. `CameraB` will be captured by the [SubViewport](https://docs.godotengine.org/en/4.1/classes/class_subviewport.html#class-subviewport) along with `MeshB`. Even though `MeshB` is in the scene hierarchy, it will still not be drawn to the Root Viewport. Similarly, `MeshA` will not be visible from the SubViewport because SubViewports only capture nodes below them in the hierarchy.

This is only true if the SubViewport uses a separate World3D, which is not the default, as explained further down the page.