You're correct about the primary inspiration for the question - besides multiple attempts to find it myself. And, yes, it's on the Sitemap page but who would think to look there?
With regard to watching out for duplicates - the person posting the question got some answers so... [shrug]
With regard to searching being more difficult one way or the other - it depends. If one uses the Google search for say "barkley family list" (one of mine), the results are horrendous! If one searches for "space barkley family list", it's the first hit.
Chris, I seriously doubt very many wikitree members would think of that, unless you add that as a hint for searching for free-space profiles.
Looking through the index may take a couple of tries to find the right range of names, and then it's useful only if the profile creator gave the page name and title some thought. Mixed results.
I understand that the wikitree crew has plenty to do. But, if someone has 5 minutes sometime, it seems like a reasonable change, and provides a link appropriate for the subject, it doesn't appear it would do any harm, and it may make it easier for someone looking for free-space profiles.
EDIT - In addition to the paragraph above - seems like it would take a shorter amount of time to add a link to a help page than (perhaps, eventually) to code, test and debug an automatic search.