Well, it's been said that he squated 550-600 pounds for reps, so it ain't that small, and if true, squatting heavy doesn't really affect the waist...look at Melvin Anthony as a example.
doing alot of complex power-driven movements like squating and deadlifting could probably thicken the waist to some extent.....look at how stumpy most powerlifters are
but genetics are what dictate waist size
i still hold my opinion that buchanon's waist is disturbingly small.....it just looks anthropomorphically incorrect