Thank you very much for your very clear, quick and knowledgeable answer!
This sounds like what I've experienced with some "VIP" clients (I don't know if there was any label or category, it was obviously very different than any C2000 or now ulti) with constant KX at the airport and access to P lounge at CDG when the P lounge was created (even when flying on code share flights operated by another airline).
Interesting to follow..