Well I can't compare it to other games since I am relatively new to "the Sims" world, but yes the shadow box move is a regular part of (some) of the sims in lifestories..usually the ones who are into body or athletic track do it more.
There is a punching bag given as a reward (when the career rewards are open), and I've noticed that the kids and adults in the two households I have, that use that piece of equipment for thier body workouts, do those kind of moves more than in my other households.
I'm wondering though if the whole SLS game hasn't evolved (i.e., improved) alot in the past few years. From reading the boards I hadn't expected much from my SLS game... but looks like those of us who have just purchased the game in '08 may be getting a version more closely aligned with the base game (rather that when it was first released)...meaning more perks/animations.
But I'm sure you can better assess whether those changes.
Of course it could just be that we are reaping the benefits of the years of wonderful creations /mods of experienced simmers