Except as provided in paragraph (2) of this subsection, the three steps available to a grievant in the grievance procedure are: Step One: the initiation of a grievance procedure; Step Two: an appeal to the head of the principal unit; and Step Three: an appeal to the Secretary. If a grievance is based on a performance rating of satisfactory or better: the grievant may appeal the grievance only at Steps One and Two of the grievance procedure; and a decision at Step Two of the grievance procedure is final. When a grievant's appointing authority is also the head of the principal unit, the grievant shall appeal the Step One decision directly to Step Three of the grievance procedure. If the basis of a grievance is an action taken by the principal unit or by the Department, the parties may agree to proceed to Step Two or Step Three of the grievance procedure as appropriate.