I was aboard 914 from SFO to IAD today and can confirm what is already speculated, it was not the new configuration.

Even the FAs were told to expect the new configuration today.

One showed me the configuration in her book that she had studied. She said the swap out occurred at 4 am this morning, no reason relayed to the crew.

I take this flight 3-4 times a month so maybe I will get lucky one day soon.