I am not sure what you are saying - but it is shorter between the poles if you go straight through the earth - about 12 000 km while a straight line on the surface (doesn't really matter which longitude you choose) is about 20k (18.5k).
The earth is also not completely spherical, so it is shorter to circumnavigate from pole to pole than from east to west (37k vs 40k km). So we shall give the flat earth at least this point. The earth is slightly flatter than a perfect sphere.![]()
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