There is more to it than that. Barbarossa had to be set back to bail Italy out in Greece- 6 weeks there. Shift troops and resupply- 2 more weeks. The russians absorbed an enormous loss of men and material in the first 3 months of Barbarossa. Russia is always tenacious on defense, less so on offense... my Grandma used to tell me how the planes would dump cargo leaving the airbase, Malstrom IIRC.