Thats because they portraied all the people as they were, they didnt look care all too much about scalling, thats how large some guys are these days, or even 15 years prior when the movie was shot. For example, in a movie like Dark Knight Rises, with 5 ft 9 Tom Hardy, they paid atention to work with camera angles, used other short actors as Bane´s mercenaries and gave him shoe lifts, so he looks like this large menacing vilain. Cam Gigandet has solid height, but he is kinda skinny, so i think in an attempt to make him look strong they tried shredded look instead of trying to put on a mass on a naturally lean frame, which would take more time and effort. If you remember Jake´s first training, he gets his ass kicked by a short dude and makes a remark how its an insult for him to be put against a guy lighter by 20 pounds. Ryan McCarthy was supposed to be terryfing for his skills, thats why they didnt care about putting in there some of his goons and i think at least on of his opponents as really big guys, but he is definitely not supposed to look smal. Anyway thats just my take on a film, take it for what its worth.