They didn't make WSL for the benefit of mankind though, they made it so that Windows would be a better, more competitive product for developers.
If Linux distro vendors want to be more competitive for Windows users then they will have to take the initiative to improve Wine, the same way Microsoft took the initiative to support Linux apps on their own platform. It doesn't make any sense for Microsoft to take both torches and kill their own competitive advantage. They would rather have people use their own platform, Windows, which they clearly believe is the better one.
If Linux distro vendors want to be more competitive for Windows users then they will have to take the initiative to improve Wine, the same way Microsoft took the initiative to support Linux apps on their own platform. It doesn't make any sense for Microsoft to take both torches and kill their own competitive advantage. They would rather have people use their own platform, Windows, which they clearly believe is the better one.