Yes - my understanding is that rather than save the entire battle as like a movie type thing, what it actually saves is the units and then the moves you make, like your orders. but sometimes I've seen it so confused that what was a close victory for me replays and becomes a loss...

No wonder I can confuse the computers troops, apparently even after watching me it still has no idea what I did, much less trying to counter it at the time on the field of battle :)