I'm just guessing, but I would think that AC wants to stop the two of us SE going into the lounge together, then you taking my bp and card out and handing them over to our non-status friend, who then uses them to come into the lounge and join us. As a way of preventing this, use of the single card to enter a single lounge on the same day sends up some kind of a red flag and prompts the agent to ask. This has certainly happened to me at YOW and YVR when I've been in and out same day for a meeting. As I said, it has never been a problem - the agent asks, I explain, end of story. Again, this is just my guess - but I've never had any queries getting into any MLL under other circumstances...