Yes, I guess that might be it. I am a bit puzzled now though because that one uses the Fredericksburg OOB with Burnside in command, default command rating of 'D' & 'E'

whereas the Chancellorsville OOB has Hooker in command with a default 'C' & 'B'
I just thought there must be a big campaign scenario for the April / May campaign using that great big map.
Also the AoP organisation changes between the two campaigns from the awkward Left, Right & Centre Grand Divisions to the later Corps structure that follows.