Yeah well, in the mod sword of damocles I decided to test this, I saved before a battle, I had 20 villainese longbowmen against 20-ish marinian infantry or footmen or w/e.
In the first try I killed myself with f3 and watched the battle, I won, I had like 10 left.
But when I used auto-resolve I LOST.
Auto-resolve FAILS, whether the player isn't there or he is has nothing to do with it.