I think neither of the countries that you mentioned can actually attain 50 slots. It is quite a large number and Brazil is mostly jungle wasteland with basically almost no slots. Poland probably have too few provinces but is the best "candidate" as far as attaining 50 slots. Czechoslovakia most certainly have less than 50 slots, they are not much bigger than Hungary for example. Sweden should definitely not have anywhere close to 50 slots, it was so not undeveloped at the time of WW2 and the population was around the same as in Austria.
So you agree with Canada, the Raj and China then? And with the other 4 I suggested I would be willing to believe: I meant 50 factories could only POSSIBLY be achievable after all relevant focuses and the max factory research has been completed, i.e., not really before 1945 (i.e., a decade in the game) at best and just barely. That's what "maybe" means, especially in a game where the devs outright said they are buffing the minors to make them interesting. Stop going solely by history people (because I AGREE that historical it was really a stretch), but in they're intended to be buffed and be stronger than IRL.