Differences between main map and strategic map

[Gribeauval]

Hello,
I have noticed some differences between the main map and the strategic map.
I play the great campaign beginning in august 1805 as french.
On the strategic map, after a few turns, I can see in Olmutz a green square which is the russian army commanded by Kutusov. I can even know approximately its composition.
But, on the main map, Olmutz is in Fog of War and nothing indicates that a russian army is present.

It happens sometimes in the other AGEOD titles (CW2, AJE, Espana36, TEAW or TYW).

Regards.