Indeed. A proxy robot war is just a very expensive game. And if you can settle your differences this way, you may as well do that in Quake 3 Arena for cheaper. And if you can settle your differences with Q3A, you may as well do that over the negotiating table. All of these depend on mutual cooperation; both parties agreeing to respect the outcome of the game.

Real war starts when one party is unhappy about the outcome and unilaterally decides to no longer cooperate.

Also when the two parties misjudge their relative military strength. If both parties were in relative agreement about what the outcome of their war would be they wouldn't have to fight one in order to negotiate changes to the status quo. That's why espionage can be a stabilizing force and the US and USSR had treaties during the latter parts of the cold war allowing each side to fly spy planes into the others territory to count missile sites.

Well, you have to make sure those spies also report that neither side would decisively win. The US and USSR must both have already been confident enough in their own strength to openly allow the other side to see it.