When I worked in professional baseball, I would watch my pitchers take their bands, attach them to a fence and absolutely go to town on their rotator cuffs. Oodles of external rotation in all sorts of different positions. And I would always wonder, does that do anything at all?
In the throwing motion, the rotator cuff works eccentrically (except for the subscapularis). Meaning the muscles lengthen. In external rotation, the muscle shortens. This is a big difference. It's like training a pitcher to throw a baseball like they were hitting a backhand in tennis.
I'm sure there is some percentage of carry-over to the eccentric contraction but shouldn't you train the exact movement?
I would always have my pitchers do the same movements but heavily emphasize that they go "slow on the way back." This emphasizes the eccentric component. Lower reps and really fight to resist the tension.
In training programs I would do the same. TRX Rows, 1-Arm DB Rows and any pulls were designed to build eccentric resilience. This is what they NEED!
When you program, you have to look at the demands of each muscle and how it translates to their sport. If we stay in baseball, we can look at the hitter's swing motion. For these guys, oblique pulls are common. When you swing your backside abs need to lengthen and the front side need to shorten. So in the weight room, you have to emphasize this difference.
Take the time to look at the demands of the sport. Then take the time to look at the exact demands of each muscle. Once you're doing this, you can start working towards making this efficient and powerful as well as plugging in the right exercises.
Applying the appropriate type of resistance in your program is a key component of the genMAX training model. If you intend on unlocking someone's actual genetic max (genMAX), you have to consider everything.