Night Movement Fatigue

[Steel God]

Curious situation.  My opponent and I started a battle in Campaign Shiloh, scenario 80 "On the Road to Shiloh".  One of the optional rules I selected was Night Movement Fatigue.  I started the game as the Southerner and moved first, it was a dawn turn.  When I got the file back I noticed all of my units had acquired a smattering of fatigue (10 points I believe) and I mentioned in passing to my opponent that I didn't realize Dawn Turns would be considered "Night Turns".  Here's the thing though, his units acquired no fatigue on their first turn. 

Anyone have an explanation?  Is the game routine some sort of weird set up with the Southerner always considered to be moving second, so when a scenario starts with them moving first they're actually starting on the 2nd part of the turn (I am stretching I realize, but struggling to grasp why a rule would effect one side and not the other). 

I don't think 10 points of fatigue in a few dozen units will alter the play of a scenario that only lasts 1 day, but it would have implications for longer scenarios.