I think they do that for anyone who may possibly be “diamond laundering” , which is just what it sounds like, money laundering using diamonds instead of currency. Since it’s usually apparently honest men just trying to be good significant others, it’s more difficult to detect .

(Yes, of course I’m kidding, I couldn’t resist. In all seriousness, I consider RNE’s advice “Any schedule change …” to be among the absolute best advice, right up there with HUCA, in the frequent flyer world.)