This subtitle does not apply to: an attorney in the General Counsel’s office; an employee who assists or acts in a confidential capacity for an individual who formulates, determines, or carries out management policies in the field of labor-management relations; a Montgomery Commission merit system employee during the employee’s initial probationary period; or a supervisor, as defined in § 2(11) of the National Labor Relations Act, 29 U.S.C. § 152(11).