For 3D printing purpose, such a shell command does not need to be anally precise. However, the resulting output does need to be able to be manipulated with 3D booleans.
I note that the V8 WIP fails here, producing the same bad result.
I need to be able to add be able to do additional work with the object after the basic shelling is complete. In the previous example, I have added a cylindrical reenforcement over a door opening and details that I do not want to complicate the shelling.