I have just been testing this out myself. It would appear there is something in it. I did tests with two different firing lanes at the same distance (long range) and vs vanilla Riflemen. Supposing the non-StG volks don't lose a model much before the StG volks (due to RNG), these vanilla volks almost always kill the Rifles faster than with the StG upgrade.
In the times when the StG volks do kill them faster it is very very close and not anywhere near the double dps at long range for the 2 longest lasting models that the weapons stats show.
Weird.
So where did this idea that it's supposed to improve their long range dps come from? The notes from the patch say:
"Added StG 44 Package. Grants the squad two StG 44s that improve short-mid range combat for 60 munitions."
Nothing about long range dps. You could argue it doesn't say that the long range dps will be reduced, but isn't that how STG44's work?