The documentation (for 3.5) states that "[PyImport_ImportModule] is a simplified interface to PyImport_ImportModuleEx()" but the current implementation calls PyImport_Import instead, which is a higher level interface that takes into account import hooks. Older versions of PyImport_ImportModule (say 2.0) did call PyImport_ImportModuleEx, but that's no longer the case.

The PyImport_Import* naming convention got a bit messy with the years and maybe I'm not understanding the intention quite well, but it seems to me that the documentation is outdated and that there is a change in semantics for PyImport_ImportModule.