Pretty sure this is a bug not intentional...When you modify gamma setting, it does not hold. Every time game is restarted the setting falls back to default 2.2. Sometimes, but not all, when starting a 2nd successive map it also jumps back to default.
Certainly not game breaking but when starting a new match it is easily seen when the gamma is back to default so you have to stop playing for a few seconds to go back into settings and reset gamma to your liking. A lot can happen in this game in those seconds.