I stumbled across this as I started a Legendary 1.3 play; I had NCE (not created equally) on during gatecrasher.
One of my rookies who had 5 hp took 1 point of damage (specifically, took 2 points of ablative damage and 1 point of actual damage on his health bar after ablative), so he's at 4/5 hp and at mission end he has a 10 day wound timer.
I remember that NCE is on and I hate it, so in the Avenger I bring up the menu and turn it off. I go back to my men: suddenly I notice that this one guy who took a wound no longer has any wound time! My hypothesis is that with NCE off, all Rookies go to 4 maximum hp (well that's a fact not a hypothesis), and then the game sees 4/5 -> 4/4 hey no wound time.
Therefore it appears you can "cheat" the game if NCE gives you a guy above the normal hp count, he gets wounded during a mission then after the mission you turn off NCE off to reduce the wound timer since it looks like he has taken less damage than he actually has.