If you look Canadian recommendations about wintering, they are almost as I have clarified.
One thing is that Canada just starts to use polyhives. They wonder "should they wrap the hives ?". No, they need not wrapping unless with a net against woodpeckers.
If the hives are under snow, they leak so much heat that the hive will be in a snow cave. Snow melts about half metre around the hive even if out temp is -30C. Then temp under snow will be about - 5C, or the snow reformulate when water vapour moves from warm to cold.