I am working with gbXML files generated by CAD, and I notice that all Surface elements seem to have their geometry described both by a PlanarGeometry child element and a RectangularGeometry child element. In the docs I see that RectangularGeometry is described as 'Geometry in a form typically used by Simulation engines'.

In some circumstances I have observed that RectangularGeometry describes a shape that differs from that which is described by PlanarGeometry for the same surface. For example the RectangularGeometry only provides a height and width (rectangular shape), while PlanarGeometry describes a non-rectangular polygon using a PolyLoop. There are some examples of this in the sample files listed on gbXML's sample files git repo.

Does the schema allow for surfaces to only be described by RectangularGeometry (not very clear in the documentation) without PlanarGeometry? What is the intended use case for RectangularGeometry?