In reality, there is a little shed under a canopy with a computer and a scanning gun to which last minute items, or items which won't "clear", are brought. If the guys with the hairy arms can't "clear" the items before "Scheduled Time minus 10 minutes", then the hold is closed and the bags stay behind.

That's why it is vital we capture a passenger at the gate and verify his tag numbers immediately if there's a discrepancy. It's not good customer service to send a passenger on his merry way without his luggage..........

(Shaddap! I know what you're going to say..............Why not? That's what you did last time I flew with you!" There! I said it for ya! )