Hello Ingo,
Thanks for those samples.
The only explanation we have so far is that your project is considered a test project. The rules you mentioned are only run on main sources and not on test sources.
In SonarLint we determine if your project is a test project by checking your project references. If a known test assembly is referenced, the project is considered a test project. This is different when running with the Scanner. Could you check if it’s the case on your side ? Do you depend on test assemblies ?
For reference this is a recent related post on Visual Studio.