Member Rara Avis
You posted your question in the right forum, Ed. It's a bug, the result of the way we're handling the MC forums.
When we expanded the original Adult forum into MC, I wanted a "one ticket" approach to avoid a whole lot of administration work. Essentially, if you had been granted access to the original Adult forum, then you automatically had access to all the new MC forums. Unfortunately, I neglected to extend that functionality to Smart Search.
My oversight has been corrected and you should now see what you expect to see.