Thank you all. I will check the 401a9 rules, which may be at play here.
The official option in the plan document is Contingent Annuity, not Joint and Survivor Annuity, so wondering if that changes anything. It seems to operate in the same fashion as J&S the way it is written.
Contingent Annuity - A Contingent Annuity provides a reduced amount of monthly income for the life of the Participant and, in the event of his or her death, an amount of monthly income equal to 50%, 66 2/3%, or 100% thereof as elected by the Participant for the life of his or her Beneficiary.