GetAll() ignores the interface passed in the D-Bus message because lookup_object_and_method() returns the last object_info in the object's info list if there wasn't a matching method on the object.

  for (info_list_walk = info_list; info_list_walk != NULL; info_list_walk = g_list_next (info_list_walk))
    {
      info = (DBusGObjectInfo *) info_list_walk->data;
      *object_ret = info;

      for (i = 0; i < info->n_method_infos; i++)
        {
          const char *expected_member;
          const char *expected_interface;
          char *expected_signature;
          const DBusGMethodInfo *method;

          method = &(info->method_infos[i]);

          /* Check method interface/name and input signature */ 
          expected_interface = method_interface_from_object_info (*object_ret, method);
          expected_member = method_name_from_object_info (*object_ret, method);
          expected_signature = method_input_signature_from_object_info (*object_ret, method);

          if ((interface == NULL
              || strcmp (expected_interface, interface) == 0)
              && strcmp (expected_member, member) == 0
              && strcmp (expected_signature, signature) == 0)
            {
              g_free (expected_signature);
              *method_ret = method;
              g_list_free (info_list);
              return TRUE;
            }
            g_free (expected_signature);
        }
    }

Thus, for GetAll(), unless an interface of the object itself provides GetAll(), the last object info in the list will always be returned, which might well be incorrect.