While i understood your point and have both 1257ad and Viking Conquest as my favorite mods for warband for the historical setting i kinda disagree with you.
Not everything needs to be "educational", we've played through Europe's map in a hundred different games and sometimes a fantasy setting adds alot to something, in the case of M&B is that it allows plausible anachronism since Calradic cultures while similar to RL ones evolved different and have their own unique twists by their lore.
For example, in a historical setting like Viking Conquest the unit roster is very limited and cultural differences are minimal because these people shared lots of similar equipments and tactics like cores of spearmen, skirmishers, scouting cavalry, elite household warriors forming a first line of heavy infantry etc, that's also why the 1257ad devs made cultures shared between many kingdoms like western european, baltic etc, they were too similar to justify the work of making separated troop trees for each of them.
In the anachronistic setting of Calradia it allows a greater range of equipment and inspiration from a broader era, they have falxmen for example that were used in antiquity fighting early medieval knights, something that didn't happened in real-life, they managed to place a norman-like faction at the same time of a "crisis of the third century" inspired event in the imperial civil war, these wouldn't be possible in a historical setting, you would need to pick a date and then mold the map on the events that really happened there.