C++20. Are build systems necessary in simple multi-file projects?

Question

C++ / C#

Before C++20, we didn't have modules, and if we wanted to split a project into multiple files, we had to introduce build systems (to link the main file with the implementation files). I had to do this even in simple cases. Do I understand correctly that this is no longer needed, starting with C++20? As far as I know, in the new standard you can safely write import <some.cpp>;and not worry about the division into declaration and implementation, as well as linking. Is this all true or have I misunderstood this part of the language?