Earlier quoted context omitted.
I’m not sure what the longer play is or how it ties into Apple building in C# or Swift on Windows, neither of which are a prerequisite to iMessage on Windows.
Well, if Apple builds an app in C# then they would probably want to use their OS to do so. In order to do that they would need Visual Studio for Mac which would allow them to work with Apple to improve those tools and open doors for developing C# applications on MacOS as well as compiling those Applications for MacOS. If Apple were to write a client in Swift or ObjC then it would do the reverse and potentially open u…
There’s pretty much zero chance that any of those build scenarios would happen. This is a hypothetical app for Windows, so it would be built on Windows, and it would use Windows tooling. No Swift, no Objective-C, no macOS. There is no reason that Apple would drag their entire ecosystem along to build this app, if they even built it themselves.