But, since the FAI's top-level goal is just to preserve human top-level goals, it would be pointless to make a lot of fuss making sure the FAI held its own top-level goals constant, if you're going to "correct" human goals first.)

Well, part of the sleight-of-hand here is that the FAI preserves the goals we would have if we were wiser, better people.

If changing top-level goals is allowed in this instance, or this top-level goal is considered "not really a top-level goal", I would become alarmed and demand an explanation of how a FAI distinguishes such pseudo-top-level-goals from real top-level goals.

Your alarm might not be relevant data, but an explanation might be possible from the FAI / the person who proved it Friendly.