I'm on record as not liking the marketing strategy. I think it's a joke and it makes my stomach turn as much as yours 404.
The reality is that KLM no longer have the mantle of the oldest airline. Just as QF wouldn't have the mantle if we 'merged' with BA to form a new company but continued to operate as QF. Of course, that may not stop them from trying but it wouldn't be right.
To be honest, I'm not normally one to get into the nitty gritty of technicalities. It means that you're probably pulling something dodgy but using the letter of the law to get away with it. By the letter of the law, QF is probably correct. I agree that it's a bit dodgy and I reckon it's a bizarre line to take in advertising for an airline. It reeks of desperation and resting on laurels- something I know the crew don't do but it concerns me if the marketers and commercial types feel that is a wise way of marketing the airline.