I have tried that. Starting in skirmish mode, taking damage, going back to campaign. It's probably just something that has changed in the code as it all initially worked with two trainer iterations ago when I first purchased the game. Then Steam updated it. Not a big deal unless a few more have the same issue. I'll live.
trainer tested with skirmish and also, as described, with user taking damage at least once before trying to turn the option on.
the best way to use the trainer due to the way the stupid game is coded (and it's 1000 patches)
is to start a skirmish, no trainer on at all, then send troops to get damaged, then once that occurs, stop the skirmish and then load or start whatever it is you were trying to really do, then activate the options at appropriate times
I have no other suggestions. It works here and all problems with this game are due to 1) 1000 patches a week and 2) the fact that code is created on the fly at times and the remnants of the pre-cache to create the code in the just in time compiler keeps copies of code which the trainer may latch onto that instead which can usually be prevented by doing what I suggested