(1) The commissioner must approve any amendment to a voluntary plan adjusting the provisions thereof, as to periods after the effective date of the amendment, when the commissioner finds: (a) That the plan, as amended, will conform to the standards set forth in this title; and (b) that notice of the amendment has been delivered to the employees at least ten days prior to the approval.

(2) Nothing contained in this section is intended to deny or limit the right of the commissioner to adopt supplementary rules regarding voluntary plans.