It is beginning to seem pretty clear that the BA Lounge attendant at IAD simply did not understand BA's own policy. I sent BA an internet complaint; their response was that they are sorry I was denied access, I should also feel free to complain to CX, my home carrier, and they then sent me a copy of BA's lounge access policy. The response was basically talking right past me because their own lounge policy makes no mention of a reason why their BA IAD Lounge should not have granted me access. It clearly leaves me with the impression I should have had access to Galleries First with CX Emerald status, card, and OW boarding pass in hand, whether or not the flight was domestic or international.
This is the first time I have ever been turned away from accessing a OW lounge as an Emerald and felt a bit helpless how to fight back when the moment was at hand. It was the first time in many years that I spent two hours waiting for a flight in a terminal with no lounge access.