I think it is a good assumption though, Solitude and Windhelm are both economic capitals of Skyrim, and are the largest and most powerful.
I seriously doubt Bethesda just randomly picked two cities. These two seem to have great importance.
"Assumption" is the key word here. By making assumptions on your map and not placing a warning, you're spreading false information. Spreading false information in the form of "assumptions" seems to admittedly be very popular among users in this forum (like how people assuming the map will be smaller than Oblivion because Bethesda said "comparable in size" instead of "bigger" are telling people it'll be smaller as if it's a fact), and if you want to contribute to this trend then by all means do so. However if you want to make an
accurate map that only gives facts OR gives a warning that you're making an assumption with something (educated guesses are often necessary after all), your map will be that much more professional. I can guarantee you that there will be someone who views your map, sees that they're the capitals of the two factions, and assumes this is a cold hard fact, when it's absolutely not. If you're perfectly fine with this, then disregard my complaint.