The way the QF system works:

OLCI per one of the various channels.

At bag drop, machine scans FF card to pick up FF Account/itinerary. Bag is scanned for e-tag. Passenger prompted by screen to confirm destination - tag is then associated with the itinerary and a bag receipt (together with tag numbers) printed. The e-tag can be scanned at any time to discover owner/destination. Similar scanners are used by check-in agents to associate the bag to the itinerary if manually checking in.

Obviously, the tag doesn't necessarily have to belong to the passenger since it is allocated to the itinerary at the start of the journey.

Regards,

BD