I think you've overlooked one issue with this statement. You're assuming the 022 as a last line of defense where opposing naval forces have dismantled PLAN's blue navy. But a skirmish in the Spratly's could be one of limited engagement. If it was China vs Vietnam, there's no endurance issue with the 022. The countries are right next to each other and the 022s can dart across in raids. In the last naval skirmish between the two in the 80s, I think only small "frigates", if you could even call them that by modern standards, were engaged in the limited battle. As for Philippines or Malaysia, the 022s wouldn't be used to reach their shores but the 022s can be based on the Spratly Islands that China current occupies. They have built little garrisons out there, why not station some 022s there to beef it up? Some of these garrisons have airfields so there is limited air cover.
Spartlys are well to deep in the open sea, that using missile FACs would only mean similar humiliation as in 1974...these boats are useless in open ocean confontrations and their capilityes comes handy in near shore, when they can use the coast-line and its geographics as suplement cover. Again, they lack the endurance and sea keeping for open sea operations. FACs in spartlys are usefull in solely defending the isles themselves, but not in practically anything else, expecially when PLAN does have better units to suit for the operations....
I Keep wondering, what sort of image do you have on coastal defences and boat size vessels capilities at first place, as you post something like this??