pretty sure its a feature, otherwise youd be seeing a floating mg retreat, why would they add the animation, although I agree its kinda silly.
MG34/42/Vickers(?) teleports the weapon to the crew. So it's not a matter of animations.
I thought that pack/unpack speed has disadvanatage in small arc of fire
There was a time we justified it because of 6man crew. So much has change (specially lethality)