I don't know if the parameter works but the location of it determines whether or not it breaks the map on game load. The examples I have are "broken"--don't work.
When I copy the format of previous maps to use in a new map, the map doesn't load on game start and the game dumps. It isn't a template just one of the planet parameters and I do most of the editing in notepad and always finalize a map in it. I have taken the entry from an older map and duplicated it in my own and it isn't functioning--game dumps on load.
If you can refer me to a map that is functional for you with the parameter I'm happy to try it.