OK, this is interesting. I can't see the photos well so I will just take your word for it. Is this general use in all of Germany? Even what used to be Eastern Germany? What is the amperage or power available at the panel? Is the range/stove water heater or other appliances three phase? It would be interesting because I have never seen three phase appliances sold here. Part of it is that we have very expensive electric rates and using gas or other fuel is cheaper.
I mean, if they wanted they could build every home here with the panel already prepared and wired for three phase but it saves a little money at building time and it means a lot more cost to retrofit. Like so many other things. I would like to have cat5 ethernet cable in every room but it would cost me a fortune now to install when it could have been done at new construction for very little.
It's general use in Germany, but I don't know what was the standard in former Eastern Germany was. For sure, everything gets adapted to the Western Germany standards there over time. So it's perfectly possible to find older installations that aren't updated to modern standards.
At this particular panel, there's 22kW available (3x 32A). Afaik, this is the common standard for a household. If one uses electric heaters, up to 3 x 63A (43kW) can be installed. But usually we have Gas or Oil for heating.
There are small boilers (2kW), single phase pluggable into a standard socket, and larger ones (three-phase, up to 24kW) commonly available. In the kitchen, there's a three-phase wire junction box for the cooktop and oven available (also common standard). Cooktop / oven combinations have a three-phase input but can also be wired for single phase usage. At older houses, the kitchen cooktop installation can be quite confusing for the beginner, since the three-phase junction box wasn't standard back then.
I have retrofitted Cat5 installation here myself, didn't cost a fortune at all, but had to be done at the right time (e.g. while renovating a room).
Now that I think about it, I was recently reading a thread in some forum, I don't remember where, where some guy was asking about connecting some heater which could be wired for three phase or for single phase and he was doing it all wrong. I do not remember the country. I assumed it was some industrial heater but now I wonder if it might have been a domestic thing.
I was assuming the price of electric power in Germany would be relatively low but I found
https://www.cleanenergywire.org/factsheets/what-german-households-pay-power which shows it is the most expensive in Europe due to high taxes. Well, I guess Germans are rich and can afford such high prices.
In Spain we have high prices and low incomes so we have to save. It would be interesting to compare energy consumption in different countries.
I find it interesting to discuss the different electrical systems, regulations and customs in different countries and I might open a thread in Chat on this topic if I feel I have the energy to write about it.
In the UK power is mostly distributed as three phase, but it gets split up into single phases, when sent to houses and small shops. Pole mounted transformers are rare and are only found in remote rural locations, such as farms, which have a three phase power supply.