I’ve been using super insulated foam hives for a few years now. Mine are homemade from 1” to 2” extruded polystyrene. I’ve tried designs with top ventilation and hives with no top ventilation. I never leave the screened bottom open in the winter. The only times I’ve seen a moisture problem is when I didn’t have a proper drip edge on my top cover and water ran under the top and into the bees. That generated a lot of mold and made a real mess.
This winter I’m running my full sized hives with mid entrances (which become top entrances in the winter). My nucs will all be running bottom entrances with a sheet of painters plastic for an inner cover; very similar to that German video. I’ve run that way this summer and so far so good.
The main problem I see in highly insulated hives in the winter is overheating during a warm spell. The bees make heat to keep the cluster warm and that does warm up a foam hive. I’ve seen hives in the upper 80s when it’s 32F outside. Problems start to occur if they get too hot in the middle of winter in Michigan. The top vent/entrance in my full sized hives seems to prevent the excessive heat while still providing an insulating blanket for the bees. Despite a common beek belief, a small hole in the top of an insulated hive is not going to let all the heat out. Just like a small hole in the top of a human house doesn’t let all the heat out.
My nucs have less bees, generate less heat, and seem to do alright with just a bottom entrance and little or no top venting. This winter, most nucs will get zero top ventilation. They will have the plastic inner cover like the German video shows and yes, the bees seal that to the hive body thoroughly.