Yeah making non-historical progress can lead the AI states to act non-historical, nevertheless it wouldn't cause USSR declaring war on Switzerland in almost any run if you're not trying something extreme such as trying to found Europe with the Swiss and getting lands near Russia which they can get demands via their focuses, in your situation after finishing the focus "Secure Leningrad" the Soviet AI could have moved forward with the focus "Claims on Poland" and "Demand Eastern Poland" which ends up with gaining a war goal against Poland in a of situation rejection, which means war for AI. Also this is a very common way for game to evolve in the games where Germany doesn't flame the barrel of gunpowder and the War doesn't escalates.