It's about navigability/discovery of the source - to find out how the sys module gets initialised, you currently have to look in multiple places. The idea of the patch is to simplify that to the one logical place: sysmodule.c

However, I'm not sure it's right to actually *move* the full import state initialisation. A simple *indirection* (pythonrun.c -> sysmodule.c -> import.c) would solve the navigability problem while also retaining some level of encapsulation for the import state initialisation.