A supervisory member of any department or agency employed by the state of Iowa shall not be granted a voluntary reduction to a nonsupervisory rank or grade during the thirty-six months preceding retirement of the member. A member of any department or agency employed by the state of Iowa who retires in less than thirty-six months after voluntarily requesting and receiving a reduction in rank or grade from a supervisory to a nonsupervisory position shall be ineligible for a benefit to which the member is entitled as a nonsupervisory member but is not entitled as a supervisory member.