Wait, are you complaining about the recoil or the barrel sway? On the barrel sway, I think the SMGs actually sway less than the rifles, or at least when they do sway, the sway is far less extreme. Rifles will really sway around a lot if you let them. I've never noticed a real difference between the bolties and semi-autos, nor between the STG, nor the SMGs among themselves. I THINK the SMGs sway a little less than any of the other weapons, but I'm not sure. I haven't done any kind of testing on that.
As far as the recoil on the PP* series of SMGs, it's extremely difficult to tell when you've only fired ONE bullet to compare to the rifles. None of the Russian SMGs have a "single fire" selector, and the sound isn't a reliable cue because the sounds are actually loops designed to play as long as you hold the fire button down (or so I recall, anyway). I think the MP-40/41 is different and actually can be fired as single shots, but that's because of the far lower rate of fire.
Anyway, I agree that sway could be dealt with any number of ways, but much of that is subjective. One person with a lot of experience shooting might not even notice what sway there was, whereas a newbie shooter might both sway around a lot and have a tough time compensating for it in real life.
Stamina MAY also have something to do with it. I think the SMGers are usually running around more than the average boltie soldier (same with semi-auto troops), so their reduced stamina MAY be affecting the sway, although I'm not 100% sure HOW it affects it (IE: does it make the sway kick in sooner, or does it increase the range of the sway, or both?).