The Director shall designate one employee of the Department to be “State Supervisor of Assessments” and other employees of the Department to be “assessments area supervisors”. Subject to the direction of the Director, the State Supervisor of Assessments and the assessments area supervisors shall supervise the performance of duties of the supervisors and the various assessors appointed under this title. The State Supervisor of Assessments and the assessments area supervisors are in the management service of the State Personnel Management System. However, they shall hold their positions during good behavior and may be removed from their positions only after a hearing before the Department and a finding of incompetency or other cause.