True. I was actually one of two people in my unit in Korea that did not cheat on my spouse. As for prosecuting it, you are correct. However, if the husband were to make a big enough issue out of it they might. No CO is just going to prosecute. Hell, the army would have no NCOs at all if they prosecuted them all for adultary.
adultery is incredibly hard to prove in civilian/military court; unless caught in the act.