> Definitely true when using VC++ with C++20 modules and MSBuild.

Lol, sorry, but as soon as MSBuild is involved the compiler can be infinitely fast and you'd still need to be waiting for the build. Also the main problem of MSVC is the slow linker, and that isn't fixed by C++ modules. This is also the first time I'm hearing that C++ modules actually help with compilation speed in real world projects - the best I've heard so far is that they're a bit faster than precompiled header but not by much, which simply isn't good enough for typical C++ projects.