I like the idea of the screened inner cover. Double screen dividers are also useful as screened covers for ventilation and confining bees when necessary.
So if they propolis the screen it's because they don't want that open I will think. If it's propolise u won't be able to see the bees when taking cover off.
Great point but this one is a very extreme example. We left it on the same hive for 2-3 years and never cleared it. So it built up. Typically they only put 20-30% propolis or around rim. But technically you would be right in that they are always building that propolis envelope around their nest. On all sides.
