Are DCA and IAD still interchangeable coterminals for flying in/out of for any fare class domestic r/ts?

Last year, I did standby into IAD when originally scheduled into DCA no problem. I know that BWI is a mileage and promotion coterminal to those two but no longer a flight arrival/departure coterminal due to lower pricing brought on by WN. As far as I recall, the only true United flight interchangeable coterminals left are JFK/LGA, ORD/MDW and IAD/DCA.

I am flying L class late evening IAD-OAK soon and would rather start in the morning and try to standby DCA-OAK connecting through ORD or DEN if availability looks good.

Thanks!

*Update: called 1K reservations and agent put me on hold to check and confirmed IAD and DCA are flight standby coterminals. Anyone done this lately?