Originally Posted by HalfEVILmonkey
My guess is he just hasn't played it long enough. Not sure if ranked mode counts towards this either, but I am pretty sure it does.
EDIT: I just checked his gamercard and he has the full 1000, so it was just an underestimate on his part.
Well I happened to get mine well before my ranked playthrough, but I went back to get a few of the collectibles on hard.