Ofc i played in HoI only with BICE mod, vanilla was too boring and empty. As far as i know AI in HoI 4 does not know what weather is. Thats why debuffs are almost useless.Either you were running a mod, or you have rose colored glasses. I ran plenty of Barbarossa attacks that started in the winter without penalties even approaching the kind you describe.
There were (and are) blizzards, which have a substantial impact, but the general weather is not as important as paying attention to supply.