Very true. The MP41 actually was one of the weapons I was absolutely glad not to see in Ostfront anymore. I mean, it was basically military police issue only.
The Problem the weapon creates in-game is that it's now very common to see it. I hardly see anyone use the MP40 anymore, if you can choose between MP40 and MP41. Why should they anyway? When looking at the two, a wooden buttstock surely implies better controlability of the weapon.
I can't tell, if the weapon actually handles differently than the MP40 in-game as I just played with it myself one or two times, but no matter if it does or not, the decision to bring it in is kinda flawed. If it is easier to use than the MP40, implementing the MP41 as an alternative choice to the former is questionable from a Game Design point of view. It's basically what you call a dominant strategy in Game Theory, as most people will always use the best choice available and thus will choose the MP41 - a weapon that was so uncommon that its constant appearance annoys everybody who is a bit into WW2 small arms history. The MP40 is dominated by the MP41 in this case. Just to compare things: There is no problem with the MP40 and the Stg44 on the other hand. Shadow costs make sure that both weapons have their own field of use and tradeoffs compared to the other, even though they are still very similar in many aspects. The MP40 and MP41 are just too similar, though (which is understandable, if you look at the weapons), making a differenciation with shadow costs almost impossible while maintaining gameplay balance and preventing dominant strategies.
However, even if the MP41 is absolutely identical to the MP40 in-game, which like I said, I can't really comment, it wouldn't make much sense bringing it in either, as the only purpose it serves then is variation as Uber_Bob correctly stated. The problem with that is that it conflicts with authenticity - something used a lot in regard to other game features by the developers. The weapon destroys some of the authenticity RO:O tries to get across, that's just a matter of fact. But this is by far not as worse as having the MP41 dominate the MP40 as alternative choice, because it's better. Still the motivation of bringing it in can be questioned in terms of development resources used. When I look on my personal list of things to add and adjust, I would have chosen some other things to concentrate on than the MP41 - but well...