He's got the guts to don the thong but that shot really exposes his box belly and how undeveloped the triceps are. Plus Zane murders him, hanky would look like a gym rat next to him.
Hankins physique is a result of his general approach to life: just show, just the talking point, no substance.
Big legs and big back come from really hard, gut busting, grinding workouts. So of course he doesn't have legs or back.
Biceps and Chest are the bodyparts every gym rat/gym bro focuses on. Those are the fun bodyparts to train. Benching and curling. So of course he has good bi's and pec's (pre-tear)
Fortunately for him he is able to maintain a low level of bodyfat. Im 100% certain that it's not a genetic disposition, but some compound he's abusing that he will never admit to.