That isnt strictly an exploit, it would make sense to retreat if you are in a bad position, e.g. to plains from woods, to make full use of army composition (e.g. cavalry).
You can have locked seeds for procedural systems, too. Each point on the map can have a fixed seed attached to it (so think of the world map like a giant grid) so that yes the maps are procedural - but they always generate the same way each time in that same spot, so reloading a battle doesn't give you radically different landscape.
Either way it doesnt look like it's ever going to happen, so I imagine the next likely thing is, one day we will see a modpack released with like 200+ rural/countryside/mountainous/forest maps all geo-locked to various points on the world map after someone comes up with a macro for converting heightmaps into terrain + randomly placing vegetation via the mod tools.