It looks to me as though you won’t get this information from the objects – not the standard GS doors anyway.
The single doors always one leaf and the doubles always have 2.
As it is not a parameter you can set in the object you won’t be able to get that information out from the object.
Versions 6.5 to 22
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision M6800 - i7 4700MQ @ 2.40GHz, 16GB RAM, AMD FirePro M6100 (2GB), Windows 7 64bit