A person retired for disability who has not attained the mandatory age for retirement applicable to persons in the employment in which he or she will be employed, and whom the board finds not disabled for that employment, may be employed by any employer without reinstatement from retirement in a position other than that from which he or she retired or a position in the same member classification. His or her disability retirement pension shall be reduced during that employment to an amount that, when added to the compensation received, shall equal the maximum compensation earnable by a person holding the position that he or she held at the time of his or her retirement. Any employment shall terminate upon his or her attainment of the mandatory retirement age for persons
in that employment. A person employed under this section shall not be concurrently employed under Section 21224, 21225, 21226, 21227, or 21229, or subdivision (h) of Section 21221.