Yes, here in Germany the two single duvets is the norm. You have to really search for double duvets and covers if you want to buy one. Special offers are always only for 135 cm width, which is the standard single size.
I once read a hotel review from a German visiting Ireland who complained that there was only one double duvet on the hotel bed. They had never seen that before.
What puzzles me is that (again going back to the old days, before fitted sheets) German beds are far larger than British ones, but the sheets are ridiculously small and hardly reach under the mattresses. I have had sheets inherited from my mother and mother-in-law on the line together to verify this!
Back before the fall of the Berlin Wall, when the area where I live was still occupied by Americans. I was talking to an American lady who had moved here and was living "on the economy" (which means not on the US compounds, but in the local community). They had been given a handbook on how to behave to fit in with the locals and she was amused to read that you were supposed to hang your bed linen out to air in the morning, but on no account after 10 am. I wish I could see a copy of that now.