Fixit must be unloaded as well even if you don't have changed anything there. The reason is simple, loading a hive means adding the hive to the current registry. If you don't unload the hives which we have added they will just be still there. This is not what we wanted because this is your second system registry and it is not necessary to change anything there.
The reason why we have to load the hive in the first case is because we wanted to edit it. I know, it is really a little bit confusing.