If the board of retirement of a county of the 13th class adopts, or has adopted, a resolution pursuant to Section 31682, then for those persons who are first employed by an employer of the system on or after January 1, 2006, the vested supplemental benefit shall be paid only to a retiree who has accrued a minimum of five years’ service credit in the system as a result of employment with the employer, except that a member who receives a disability retirement that is service connected is not subject to the five-year service requirement.