User blog comment:Rappy 4187/Technical Update: June 29, 2016/@comment-244709-20160630200444/@comment-4129195-20160701164411

Top contributors shows only those that made recent edits, while achievements show how much a person has edited, since they joined at one individual Wiki community.

So it does sound different. Besides, why not increase that competitiveness? At least as a temporary, since I doubt it will do anything permanent.