As an aside, I would hope that at the Centurion lounges, they would swipe the card and that the system would tell them if the card was or was not eligible for complimentary access, rather than have each agent make the decision individually. Like in the case of the OP, there are too many corner cases with all of the various Amex products issued worldwide by a variety of institutions to expect that each agent could be 100% accurate in applying the rules.