Valour does increase accuracy, but not by any important part.
I tested V0 Archers and V4 Archers against 100 V4 Pikemen with ten tests of each, with no elevation and no rain or wind.
The result was strange as the V0 archers killed more Pikemen... So in MP we most certainly can't see any difference. In SP we can possibly detect something.

Also I heard from Puzz3D that the CA did a cahnge when they made MI and that lowered the benefit of accuracygains from Honour... that was carried over into MTW.