Not once have I ever had to interact with these technologies in a way that would benefit from my application using the same language. The language they are written in is irrelevant.
You haven't had to or refuse to? I've interacted with plenty of C# teams in my career and getting them to step outside the box to solve an actual technical problem in a reasonable way is _painful_ for this very reason.
They'd rather set up a meeting or hire more consultants and stonewall a project for over a year.
Most programmers can learn and pick up C# in like a day, but Windows-based developers seem to have a lot of trouble going the other way.
What does that prove? it proves that no single developer's anecdotal evidence can be used to validate a broad-brushed claim like "The language they are written in is irrelevant."