I know of several caches that are solely based on FTFs. At least one in Michigan, and at least one in Indiana. I am almost positive that this isn't a new or updated rule, just a rule that appears to have been ignored by a few hiders and reviewers.A challenge cache should recognize the completion of a personal achievement, rather than the winner of a competition. For example, a challenge cache based on "First to Finds" is a competition between geocachers, and is therefore not publishable.
I am pretty sure there are enough examples to bore everyone, but I would just like to see everything consistent. All of the reviewers should be on the same page. If it is not allowed, as per the rules, I should not be able to go to Indiana or Michigan and be able to find one.