Don't the staff of Xinzheng Comprehensive Bonded Zone (customs coordinator, entry-exit inspector) belong to the career establishment? But why did he say reference institution?

Just a good salary reference. The key is not the people in the system. They signed an employment contract. To put it bluntly, it still does not belong to the organization. They may be fired at any time after the contract expires. As long as you work there, you can pay according to the institution, but people can cancel the contract. However, the formal employees of public institutions can't terminate the contract casually, and they have to go through examination and approval. So this is the essential difference. What is the use of salary reference? Benefits are not referenced. They will be paid after the formal work.