Notwithstanding Sections 21353, 21354, and 21354.1, if the modification to the federal-state agreement occurred on or after July 1, 1971, whenever the fraction of final compensation is reduced pursuant to Section 21353, 21354, or 21354.1 because service of a member has been included in the federal system, the reduction shall apply only as to service after the effective date of the member’s coverage under the federal system. This section shall apply to those members whose effective date of retirement is on or after July 1, 1971.