Is the person placed by the government's letter of introduction part of the unit's supernumerary staff?

Belong to. Non-staff personnel refer to those who have not entered the establishment. It means that in many institutions, because of the workload that the original staff can't bear, the unit will recruit employees outside the establishment. These people are collectively referred to as supernumeraries. The supernumerary personnel are not recruited by the organization department or personnel bureau, but by the employing unit. Therefore, the personnel placed by the government in the letter of introduction belong to the overstaffed personnel of the unit. Non-staff personnel can usually be divided into workers, contract workers and temporary workers.