Hmm... That spec doesn't define what an "interior ring" is or what a "hole" is. In fact, [grepping through the entire specification](https://github.com/GeoJSONWG/geojson-spec/blob/master/geojson-spec-draft.rst) yields no definition of "interior ring" at all.

Is there a reference implementation for GeoJSON somewhere that can clarify things? I still think the xoring approach would yield a more useful behavior that can be directly created in vector drawing tools like Inkscape (it's the object "exclusion" merge type) and would yield a very simple merge algorithm that doesn't have to treat inner and outer geometries differently.

I wouldn't think they'd ignore the past 30-some years of graphics research on this. (I know, I know, it's the JS community, but still.)