There's nothing non-standard happening there. The compiler is allowed to translate #include -> import. Here's the standardese expressing that: https://eel.is/c%2B%2Bdraft/cpp.include#10.

I do agree, it's not _exactly_ the same as using _named modules_, but header units share an almost identical piece of machinery in the compiler as named modules. This makes the (future planned) transition to named modules a lot easier since we know the underlying machinery works.

The actual blocker for named modules is not MSVC, it's other compilers catching up--which clang and gcc are doing quite quickly!