This is very interesting.
I loaded up my own save game from april 1941, about halfway into the war focus against USSR.
And I loaded up the USSR to see what they were doing.
They are making 9 inf / 3 artillery infantry units. Which is too much artillery. It's a terrible defensive unit perhaps.
Maybe that makes sense based on your thesis that they have basically programmed the USSR to act as like a zerg rush kinda country...but they need to be defensive at first.
While the vast majority of their existing infantry has support artillery only, that's it.
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But what I noticed is the AI has their battleplans set to activate before the war! So they will immediately lose their entrenchment and attack the attacking Germans?!
I'm actually impressed by AI battle plans (including an amphibious invasion into a Romanian port!), even though a lot of their army is guarding victory points.
Also USSR (sometimes china too) runs out of manpower because they have the wrong policy set!!! That shouldn't happen for majors, much less mass assault countries.