It's not crazy, it's just what happens if you write mostly C with some conveniences where they actually make sense instead of "modern C++". I generally write very performance sensitive code, so it's naturally fairly low on abstraction, but usually most of my projects take between one and two seconds to build (that's a complete rebuild with a unity build, I don't do incremental builds). Those that involve CUDA take a bit longer because nvcc is very slow, but I generally build kernels separately (and in parallel) with the rest of the code and just link them together at the end.

Sure, C++ is heavy for compilation, there's simply more by the compiler to do, but code repository building under 5 seconds is at the very low end of tail so making the point about someone bearing with the 5 seconds longer build time is sort of moot.

I wrote a lot of plain C and a lot of C++ (cumulatively probably close to MLoC) and I can't remember any C code that would compile in such a short time unless it was a library code or some trivial example.