I’m not going to believe that without a good source. Testing in Germany is at 5000,000/week now, so anyone admitted to hospital would definitely be tested. A friend of mine here in Berlin had symptoms. They called and a team came to their place the next morning. One day later, they were called and got the test results (negative).
The explanation for the relatively low fatality rate I’ve heard is simply widespread testing catching many mild cases and relatively young patients because a lot of initial cases at least were linked to ski holidays and carnival events. Personally, I would add the hypothesis that Germans have far fewer interactions with family members across generations than especially Italy, but also the US. No one I know lived with their parents after finishing school. In the US, when Harvard shut down for the semester, the undergrads all went home to family. Here, students tend to live in regular apartments. And even those in student housing live there year-round, instead of vacating them during breaks and heading home.
I believe Austria and some other smaller European countries are also seeing at least similar CFRs, making Germany somewhat less exceptional.