Apologies for taking so long to post this update. I was away for a few days and then my cat got sick when I got home. All is well now and this fairrieanum has both blooms fully open. It has two new small growths at the base of the plant so we'll see what happens with the next blooming.
It had one flower when it bloomed for the first time but as I recall there was a very small second bud that didn't do much of anything and eventually blasted. Maybe you're right and this one is genetically programmed. It came from Paph Paradise so I'd be curious to know if any of the other fairrieanums from there are also producing double blooms.