Lot of ‘Harkins is super’. It’s obv more than stats but lot of hardons here For a guy who is completely mediocre.
Game score isn't a measure of who is "good" or "bad". It's a measure of the impact each player had on the results of that particular game. Players who are on the ice for goals for end up rating higher in game score. Players on the ice for goals against get rated lower. Drawing or taking penalties are factored in as well.
It's a way to see who impacted a particular game, but doesn't say much about a players' overall ability. (Which really should be obvious just from looking at where Crosby and Karlsson ranked on that chart!)