mingw32 is the only native Windows build we have right now, but it's not inconceivable that we might have an even-more-native build in the future, by bypassing mingw32 altogether. The Windows build might be made using mingw32, but it runs natively without relying on mingw32, as far as I can tell. It certainly runs on my windows OS without having mingw32 installed (other than the bits ghc installes additionally).
The WinHugs is now a genuinely 100% Windows build, using Visual Studio - only the libraries are preprocessed under Mingw32.
I guess I'm saying mingw32 doesn't really do much harm, and it's "correct" in some sense, but we should also have provided #ifdef win32_HOST_OS for those cases when you don't care. That would be nice.
Thanks Neil