A PICC is, in the eyes of the CAAC, a fully qualified Captain. ALL check rides, either on the line or in the Sim are PIC. There is no such thing as a PICC as far as China law. When a flying with a heavy crew, The "Captain" logs 50% of the trip as PIC and the PICC logs 50% of the flight as PIC.
Why do they have PICC's? He's a cheap Captain. Will they ever upgrade? No
It's something the companies use to under pay a pilot that has the exact qualifications and sometimes more, than the PIC getting thousands more a month.