Training function matters in functional suspension training because straps are only useful when they make bodyweight movement easier to scale, control, and repeat. A suspension system can support rows, presses, squats, lunges, planks, fallouts, and assisted mobility, but the value comes from how those exercises fit the plan.
Good training function means the setup has a clear job: adjust resistance through body angle, support a movement pattern, add appropriate instability, assist range of motion, or make a compact routine easier to follow.