Earlier quoted context omitted.
Max or close-to-max achievements for a game also is an indicator of skill, could be used to weight a games scores more towards "recommended by skilled players" vs. "recommended by casual players" ?
I would have a hard time equating achievement coimpletionism as skill, to me they are more of a measure of time spent in a game. Yes, some achievements in some games do require a mediocrum of skill, but most of them do not; they're used primarily as a form of feedback for the developer on how people play their game, and secondarily as a lure for completionists who want the points on their profile.
It only dawned on me today that achievements aren't really for the players, they're the gaming equivalent of Mixpanel, allowing developers to see which parts of the game players are actually experiencing.