This is because the Request class' constructor splits the URL into __original and fragment:

    def __init__(self, url, data=None, headers={},
                 origin_req_host=None, unverifiable=False):
        # unwrap('<URL:type://host/path>') --> 'type://host/path'
        self.__original = unwrap(url)
        self.__original, fragment = splittag(self.__original)

And the construction of object that urlopen() returns has its geturl() returns the request object's __original field (by now, minus the fragment).