As I said, the module system in C++20 is literally the Microsoft model.
Clang had another model that was rejected, and most of the years in committee were actually about finding a compromise between Microsoft's and Clang's approach. In the end, Clang wasn't particularly happy about the end result either.
Clang modules were basically "let's try to automate precompiled headers". It lacks the isolation offered by proper modules. Even if they're not faster, the isolation is something I'm looking forward to.
I'm positive there has been nontrivial work to support C++ modules going into MSVC, msbuild, VS, MS STL, etc., since 2019. And there is still plenty of work to do, for instance helping build systems know when they need to produce more than one IFC for a given module (right now build systems assume modular C++ code is ODR bug free).
