Any such reversionary annuity contract shall contain the provisions specified in RCW 48.23.150 to 48.23.190, inclusive, except that under RCW 48.23.150 the insurer may at its option provide for an equitable reduction of the amount of the annuity payments in settlement of an overdue or deferred payment in lieu of providing for a deduction of such payments from an amount payable upon a settlement under the contract.