I think the decision is absurd too, but how does this generalize to history books? They don't portray one group as "the enemy" and good practice is to actively avoid that.
I think they do, although that's probably fine. Germany was "the enemy" of the Soviet Union, as was Japan. France was "the enemy" of pretty much everyone else in the Napoleonic wars. There's nothing wrong with labeling someone as "the enemy" of someone else, as long as you don't include a value judgement.
I doubt this game labels "the vile Germans" as "the enemy of the noble Soviets".
