If the Earth was Flat, it will ease us to calculate anything especially related to spatial context.
But unfortunately no one help to prove it that the Earth is Flat.
So if you are Flat Earth Enthusiast, you are on the right side.
yes, FE should develop their own theories about coordinate system used in FE, as far as the Map they always to brag is just a conic projection of earth centered in north pole, like what we found at UN logo,
but I guess they wont bother,