I would just watch if for yourself rather than read reviews. For one, the doc calls Stalin a brutal dictator and does not shy away from Soviet reality it simply highlights the protectionist concerns that drove many of its decisions. And the non-aggression pact with Hitler was absolutely to buy time given that the West wanted no part in war with Germany early on....Hitler and Stalin hated each other more than anybody else. I think the reason he calls it "untold" is simply b/c it highlights the impacts of the US on effecting the various conflicts it was engaged in as opposed to just presenting those as evil and us as reacting to them like highschool history does. Probably over compensates a bit but the first 3 episodes have been pretty good and not that controversial imo