It is old debate among historians (and even forum posts) as to whether Stalin would have attacked Germany.
Those scholars purporting to say 1941 are very unpersuasive. But there is quite a bit of reason to believe that 1942 or 1943 may have seen a Barbarossa in reverse. (Just think if no Barb AND Germany is at war with US in 1942. Stalin would have been all over that!)
So the game event makes a lot of sense - both historically and for gameplay reasons.
By the way, kudos to developers for the new dynamic of bad relations potentially leading to a premature DoW. That actually changes an awful lot and adds a nice new dynamic to things.
Those scholars purporting to say 1941 are very unpersuasive. But there is quite a bit of reason to believe that 1942 or 1943 may have seen a Barbarossa in reverse. (Just think if no Barb AND Germany is at war with US in 1942. Stalin would have been all over that!)
So the game event makes a lot of sense - both historically and for gameplay reasons.
By the way, kudos to developers for the new dynamic of bad relations potentially leading to a premature DoW. That actually changes an awful lot and adds a nice new dynamic to things.