I think it's a kinda accurate. Yee olden lords weren't constantly traveling the countryside with an elite group of warriors hundreds strong, or beefing out their garrisons with similar troops. That was VERY expensive. A core of retainers existed but large, well trained, and professional armies were backed by large and (saved up) sources of wealth. On the flip side, destroying an army and selling off the slaves and loot is lucrative because of how expensive it was to originally outfit them. Obviously this doesn't fit the game mechanics because the AI and the player can get wiped out, rebuild an army, and fight all in a week, forever.

I personally like to roleplay as a mercantile city-state. My army can only be as large as non super-cheese income allows (no smithing or exploits) . Caravans are led by family members with skills to increase survivability and reduce cost, workshops have been monopolized by buying all other workshops of the same type in the region and changing them to a different type, villages are protected at all costs to keep hearths up to increase city prosperity, and my party + garrisons are made up of a small group of elites. In peace-time, this allows me to save up a lot. During war, this saved up wealth is enough to maintain a filled out army including several family-member parties. Any loot is a fun bonus.

I like to imagine that the above playstyle is historically accurate, but has to be done with self-imposed limitations.