

That’s a very old way of thinking of things. C# has been cross platform for a long time.
Almost everything ever written in C# uses Windows-specific APIs
Not really. Most C# apps use .NET (since the framework and standard library is quite feature-rich) rather than direct Win32 calls, and .NET is cross-platform. A lot of web services are written in C# and deployed to Linux servers.
basically no one installs the C# runtime on Linux anymore
You can compile a C# app to a single executable that doesn’t require the framework to be installed.
Are you running Jellyfin, the *arr suite, slskd, or Technitium DNS? They’re all written in C#.
They also can’t do that in countries with workers rights. This should be a standard right, not something that requires the workers to unionize.
Edit: I understand that unions make it easier to enforce.