I totally believe that would be true for the standard library--code which itself has no dependencies, is always unchanged by the user, and could frankly come first in essentially any build--but... is that also true versus a precompiled header, which always seemed to work fine for the standard library? The entire concept behind modules for your code seemed like it would limit, not improve, scalability. Put differently: what changed?
In C++23 it takes less time to import the whole standard library than a single major include like iostreams.
Currently only available in VC++ preview, though.