For example on wikipedia for Switzerland it says the country has an area of 41,285 km². Does this take into account that a lot of that area is actually angled at a steep inclination, thus the actual surface area is in effect larger than what you would expect when looking onto a map in satellite view?
I don’t know the precise answer, but I do know this:
So form my point of view it would be almost as if we tried to include the sides of a ravine or gorge in the measure just because technically it is area space.
Sorry if I cannot give you an exact answer, but I wanted to comment because you raised an interesting point that made me think.
Cheers.