You can 100% work your way to a senior position without ever leaving windows. The people who are like that just don't tend to be hanging out on platforms like HN.

To be clear, this was developing software running on *nix environments, and they were all using Mac (or WSL) and the usual open-source *nix dev tools. This is not a case of developers purely targeting Microsoft environments (indeed it would be excusable in that case).