I'm also going to guess that the distinction between the relative amounts of myofibrial and sarcoplasmic hypertrophy may be contributing, as well as diets that are geared toward maximizing apparent size (for actors) versus maximizing power relative to size (for fighters).
...and also a strong lower body generally isn't very important for a tv/movie star.
Edit: I notice you posted the same thing in the S+C forums, and those guys have handled the issue pretty completely. So there you go.
Last edited by TMMAray; 01-06-2013 at 08:55 PM.