NHL 13 is using a different rating system than all the previous versions of the series. The EA SPORTS NHL 13 blog has a great post explaining the new system.
The scouts base players off individual skills and not by how many points they accumulate in a season. Relying only on stats would leave too many variables in play, including line mates, ice time, strength of competition and so on. By creating ratings based on individual skill at every attribute our scouts are able to more accurately capture the abilities of a player as opposed to artificially inflating them because he happened to have a great year and everything happened to click for him.
Read the full post here.