He used 14-3 cable to bring power to a double-gang j-box; the red and black conductors are each connected to a separate 15-amp breaker at the service panel. One breaker is marked for the disposer.

From this j-box, he ran 14-3 cable to the dedicated disposer outlet. The black conductor is hot. Was there a special purpose for using 3-conductor cable at this location? If so, what should the box dressing look like?

Thanks in advance for any and all advice.