I will jump in to provide a response.
Just to be clear with respect to when an optional survivor benefit is established, the actual funds that are now taken by the annuitant making that decision never actually leave the pension fund. It's not like in a divorce where you would receive in the division of assets a cheque for an amount of money.
While there is a reduction of payments to the annuitant, those funds are still in the pension fund. That means that, in the event of the death of a spouse, they may revoke the optional survivor benefit and, therefore, the pension amount received by the annuitant goes back to 100%. While that benefit had been set up, the annuitant is not going to suffer on the death of their spouse.