According to OMAAT, D3 is only partially correct when a passenger visits the lounge corresponding to the booking class under general conditions. In other situations—such as my case, where I was flying in Economy Class but accessing The Pier First Class Lounge—my frequent-flyer programme (Iberia) bears the cost of the lounge visit.

At the same time, if I credit the flight to Cathay, Cathay would retain the mileage liability internally. In other words, my lounge visit would be paid for by Iberia, while the miles would be credited to Cathay.

I am trying to understand why, in a situation where the lounge cost is borne by Iberia and the mileage credit goes to Cathay—seemingly favourable to Cathay—lounge access was nevertheless denied. As a result of this experience, I will no longer credit flights to Cathay and will instead credit all future flights to Iberia.

Moreover, if I were to fly in Business Class and continue crediting flights to Iberia, Cathay would incur even higher partner-settlement costs, as Business Class mileage accrual rates are higher. This makes the outcome even more counterproductive from Cathay’s perspective.

Can someone explain the rationale behind this outcome?