I remember asking this very question when RTW first came out and it was answered.
Essentially STW and MTW held battles on one from a library of pre-rendered maps. Essentially, for the replay, the orders on the field and what occurred are replayed on the same map. Thus the fun side effect of the outcome of replays changing after patching up...
But in the campaign game in RTW the maps are generated dynamically the first time you have a fight in a particular location (per game session??). The reasoning was that they could not guarantee the same map would load for the replay and thus it would be garbage. Now the historical battles are played out on pre-rendered maps and thus they can be replayed.
Now as this is basically the same enigne I will guess the same limitation will apply...
Bookmarks