To me, it seems like obvious behavior. What exactly do you think is inconsistent here?

Of course, the default inherit-class is "what's usually known as builtins.object", and it's always the same class. You should not be able to change it just by rebinding builtins.object to something else. Just like you shouldn't be able to change the top of exception hierarchy by rebinding builtins.BaseException, for example. :-)