2) alot more shipyards can build them (remember those ubiqitous 037 class corvettes?)
3) China has 2 sets of unique challenges, much of its northern coast is bottled in by other countries. so it needs patrol corvettes just to economically serve as screening and ASW patrol fleet. similar to baltic sea countries.
But it also looking at some serious power projection requirements in the future, i.e. protecting its sea lane of communication, requiring large surface combatants.