Considering the range of the YJ-12's, you don't need to have a lot of plane range before you touch someone. In fact why bother to launch them from planes at all, you might as well launch them all from ships. It would be a lot more cost efficient. The duty of the planes would be to spot for the missiles, and to protect the spotters.
True, but having the capability can be important simply as a tactic to make it mandatory for potential adversaries to plan to counter that capability and in the process allocate resources for that from somewhere else, complicating matters for them.
Without such a capability, adversaries just need to guard against PLAN ships, but with such a capability, anywhere a J-15 can potentially reach via air-refueling is a danger zone, pushing adversaries even further away.
So just getting the information from PB out into forums or a future picture of a J-15 with two or 3 of the missiles could be a significant chess move itself.
Of course when catapults come online and with improved engines it may become official loadouts and not just a chess move.