[Moppie]

I like your first analogy, but I think you could apply it to both cases.

The difference being the packaging around the stereo more room to different shaped stereos into. It might not hold them perfectly, but they will fit in the hole with out damaging the packaging, and if you need to you can stuff some paper around the edges.

It just happens that RWD stereo packaging has bigger holes that will hold a wider variety of different stereos, than FWD stereo packaging which will usually only hold the same brand of stereo.