Correction to this statement: “CabWriter moves component entities to the component’s layer, instead of leaving them on layer 0. I went to a SketchUp training a few years ago, and they said one of the cardinal rules of SketchUp was to leave entities of components on layer 0; only the component itself, and sub-components should be put on another layer.”
CabWriter does not move component entities to a layer other than Layer0. It is the process of exploding a component that moves its entities to the layer that the component resided on before using the Explode tool. You can check this out for yourself. Choose a CabWriter component and unlock it. The use Edit Component and examine its entities and you will see they are on Layer0. Now Explode the component and you will see they have been moved to the layer the component was originally on.
I have never understood why SketchUp moves the entities when the Explode tool is used. But it does. When I teach SketchUp I hand out a FAQ (attached) and on page 10 is the topic “Beware of Context Menu Explode!”. It is a real source of problems for beginner SketchUp users.