Star ratings don't reflect the game. Even bad player can have a good game and good player a bad one. Star ratings reflects overall quality of the player. But it is influenced by the showing in the particular game - at least I believe so.
Boxscore is a good lead to find out an actual height of some attributes (FT, handling, passing, rebounding, blocking, JS/JR) however I don't how accurate it could be because it is a guess based on one game.
Moreover - you can't really see defense in the boxscore. I would be easily convinced that the difference between the numbers in boxscore and the rating reflects defensive abilities (OD or ID or both) to some level.
Maybe someone more experienced could correct me?