QA: Isn't it strange to turn comb upside down into unnatural position?

Yes, for most World's beekeepers that sounds weird. It is also hard to except by the beekeeper that wants to be as much as it is possible to the natural situation in a hive. In the past that was also hard to except by Slovenian beekeepers as well,  but nowadays many are practicing that. Many questions arise from the beekeepers like: (1) wouldn't drop out fresh honey from the cells, (2) wouldn't have larvae problems staying in the cells. I'd like to play with demonstration that even water will not flow out of the cells if the comb is turned in horizontal position and cell are facing straight down. Also larvae don't have a problem to develop and also bees for feeding the larvae. Of course, typical frame from the Langs' hive can't be turned upside down. I'm experimenting with new frame design that I will be able to use in my new experimental hive for AŽ type of beekeeping. I'm using plastic tabs to hang the frame in Langstroth hive body and I have a chance to re-position taps to other side and hang the frame back in the hive in the way that empty space to the wooden bar is on the top. Bees usually fill such gap with beeswax cells and reinforce the structure. This is grate during extraction if such comb become comb in the honey section of the hive. In AŽ hives we don't need to handle with the taps, we can just turn around the frame. We have two possibilities, just horizontal flip or diagonal and turning also front side to the back along with upside down. This usually brings honey reserves on the comb toward hive entrance. Bees instinctively remove food source from entrance side to the top and the back. In this way we are stimulating bees to use reserves from frames in brood section and to enlarge brood area.  In this way we are also enlarging comb area for two rows of the cells. If we are doing that during regular examination the such action doesn't mean extra time. In general I prefer completely build comb in the whole frame.

My experimental frame prepared for upside down position in my experimental Langs' hives that are used to practice transfer into AŽ type of the hive.

Oh, flipping of the frames  for extra comb building need some fresh nectar flow that bees will do it well. When you are rearranging the brood location regardless flipping changing the position, enlarging space for brood be aware that bees need to take care for proper thermoregulation. Don't do that if it is expected significant drop of temperature in next few days.