Just to give the OP a fuller answer to some of his Qs. The Departure Management ("DM list" as it's often called in FT or UA parlance) system is a part of United's software designed to manage several aspects of the boarding process of flights. It logs and prioritizes (if needed): 1) standby requests; 2) upgrade requests; and 3) denied boarding queue/voluntary denied boarding pax.

Because it is a DM program (emphasis here is on the word "Departure", its authority is with the gate agents -- not the RCC or c/i agents. As noted, a good RCC agent should offer to liaise with the gate but when the RCC has been busy, or I had a special interest in my choice(s) on the DM list, I've willingly run over to the gate to check things out and, if OK with the gate, left word that I'd be in the RCC