You're right about that. I've always said that if the "Smiley Face" logo had been around back then, it would be placed prominently on every after-action report. Very few officers could resist being a little self-serving when writing their reports -- Robert E. Lee comes to mind as an exception -- so I suppose it's just human nature to try to put the best face on things. I guess we'd call it "spin" these days.
It is interesting, therefore, to read the spin that the Union and Confederate commanders put on their respective reports of the same battle. In general, the truth lies somewhere between the two.