One of the intended use cases for Py_mod_create is to return instances of ModuleType subclasses rather than straight ModuleType instances. And those are definitely legal to define:

>>> import __main__
>>> class MyModule(type(__main__)): pass
... 
>>> m = MyModule('example')
>>> m
<module 'example'>

So it isn't valid to skip calling the cleanup functions just because md_state is NULL - we have no idea what Py_mod_create might have done that needs to be cleaned up.

It would *probably* be legitimate to skip calling the cleanup functions when there's no Py_mod_create slot defined, but then the rules for "Do I need to account for md_state potentially being NULL or not?" are getting complicated enough that the safest option for a module author is to always assume that md_state might be NULL and handle that case appropriately.