Why it's on the list: Why two rear-delt exercises on the list? Because these small muscles are often undertrained but are important for both posture and rotator-cuff health.
A bent-over version with dumbbells is great, either freestanding or with the head resting on a bench. Just don't cheat and sling the weights up with poor control! If you're hitting the rear pec-deck machine, use a neutral or palms-in grip—not palms-down—to maximally activate the muscle.
In your workout: This is a great move to do later in a workout for 10-12 reps or more per set, either on its own or supersetted with lateral raises, like in The Simple Workout for Super Shoulders.