> The reason that you don't have intra-module distributed build is because the intra-module code dependencies are implicit - there is no developer-defined partial cross section of the code, all of the code needs to be pulled in and semantically evaluated as a unit.

And this seriously somehow doesn't seem like a problem to you? My massively distributed (to AWS Lambda) C++ build compiles at the speed of the slowest single translation unit. You seem to be optimizing for serial compile performance, but if you truly want speed you have to go parallel. These explicitly-managed "cross sectional sunsets" are what makes this so easy to do with C++.