Hello,
This is a limitation of the map functionality, for which I don't have a solution.
Both (North) Sudan and South Sudan will be coloured if you own a coin from (North) Sudan, independently of whether it was minted before or after the split of South Sudan in 2011.
The same holds true for West German coins, which will colour both West and East Germany, even if minted before the unification.
And more generally, the map is inaccurate for every country which borders varied along history.
Ideas related to adapting the map to the various time periods are discussed here and here.