Pinching shoulders back

i heard that when working out your upper body your should roll your shoulders back and pinch them back because its supposed to take the stress off the front of ths shoulder. is this true and what about just everyday i have rolled forward shoulders should i work on pinching my shoulders back with my back?

I read somewhere the Japanese have been known to have their pitchers walk around all day with a chopstick pinched between their scaps to strengthen the muscles in the back.

The NPA often has pitchers pinch their shoulders together while doing various warm-up drills (e.g. arm circles).