This would be very useful for China to secure and shut-off much of the underwater entrances along the First Island Chain from access by enemy submarines.Underwater guerrilla warfare and ambush. UUVs are strategically deployed at certain shipping lanes and choke points, where they use acoustic decoys and other methods to lure enemy submarines into traps. Once enemy submarines get within range, UUVs launch torpedo attacks and then quickly withdraw and sail to the next area to set up traps all over again, a kind of underwater shoot-and-scoot tactic.
Besides, these UUVs can also be stationed around entrances of enemy submarine bases, and have them sitting on the seabed while waiting for enemy submarines that are leaving the base or returning to the base before launching ambush attacks.
However, for enemy submarine bases located very far away from Chinese shores (such as Guam, Sydney, Varsha, Pearl and Kitsap), using conventional propulsion wouldn't be sufficient. That means mini nuclear reactors (such as designed to propel ULR torpedoes) would be required for UUVs tasked with faraway missions.
Furthermore, these UUVs must be able to operate and conduct missions autonomously for long durations of time too.