The last factor has to do with game balance and historical accuracy. Automatic and semi-automatic weapons were not the mainstay of the armies involved on the Eastern Front. They were leavening for the bread, what made it complete. The bolt action rifle was the main weapon on the battlefield on both sides. But it was an anachronism, a hold-over to a past war. Hence both sides started out with modified versions of the same rifles their fathers carried in the Great War. The Gewehr 98 was shortened to become the Karabiner 98k and the Mosin-Nagant Model 1891 became the Model 91/30 before being shorted further in the last two variants.
As to your second point about barrel wobble, that's a game balance factor and not realism. Accuracy varies from rifle to rifle as well, the shorter bolt-actions are less accurate than the longer barreled SVT-40 or 91/30, both in game and in real life.
As a gamer I want the best overall weapon I can get in game. Maps vary so what I need varies with it. However, the semi-auto rifle fits well on any map, even for close in fighting. Bolt-action rifles do not. I'll use one if I have to but the first chance I have to pick up a better weapon, enemy or friendly, I will toss the bolt-action rifle away.