Some people might say, "Well, how do you feed all these people" but feeding 1,000,000 extra Europeans for a year isn't going to sink Germany. They were able to feed the rest of Europe, and let's be honest, the starving our of Jews and such was a policy of intentional genocide in the beginning, not the result of imminent mega crisis, though indeed a crisis was brewing. After all, employing a million Russians to fight keeps half a million German men in the farms and factories, so ultimately food and production is not the issue.
The main issue, as others have pointed out, why not rather arm Germans instead of Russians. They are more reliable. Plus, the whole victory disease thing.
One thing I can imagine is if we have ASB "unstupid" Nazis, is if they thought they were doing really well, they might intentionally raise up a "White Russian Army" as a means of hunting down Communists and causing problems in Siberia. So, victory disease might have led to serious plans to use these Russians so that way some Germans can really "be home for Christmas" when Germany "wins the war" before the winter.
Then, with the disaster in the winter, all of the sudden the Germans have this relatively large contingent of soldiers which they will need for entirely different reasons.
The result is that they are used as Ostlioggen were OTL. That means, static fortress troops in the west, fighting partisans, and the like. It frees up quite a bit of Germans to fight in Russia, and there would be earlier Waffen SS conscription of Ukrainians and such.
So, obviously it is not a war winner (the moment the US enters Germany loses, if the US never enters Germany wins). However, it would essentially give Germany a net gain of half a million men over the course of the war. So, it buys them maybe six months, long enough for A-bombs to drop.
THe most interesting butterfly is that it totally changes the German occupation of the East. It is not necessarily going to be less cruel. Russians can be very adept at being excessively cruel to other Russians and ethnic Slavs in the USSR. However, German policy would likely be much more political, with the purposeful balancing of Kulaks and such with the WHite Russian army behind them versus everyone else. Then, when the Red Army comes back, like Ukraine there will be a good deal of the USSR fighting their own partisans behind enemy lines.