I don't know when the recently posted photos were taken, but every post-refit shot I've seen has had the two racks holding two missiles each, and two racks empty. I expect a full load would be eight missiles, yes. But if there is a shortage of the new larger missile, why not just add some of the YJ-8X racks/missiles back and carry a mixed load?
Well even the 052Cs were often sailing with only a few missile tubes loaded for its slant launchers. And I doubt all the VLS cells on China’s new warships are always fully loaded.
Could be that the PLAN just prefer to keep their munitions in storage rather than loaded on ships during peacetime.
I am sure that despite the protection offered by the launch canisters, rattling around onboard ships going out to sea isn’t doing the missiles any favours; and they will have shorter shelf lives compared to if they were stored in perfect conductions in some air conditioned military warehouse.