The tracking number is on the label. There’s a tracking number as soon as the label is created, before it’s ever printed or slapped on a box. Whether or not a customer is given the tracking number when the label is created is a different story.

I’ve had plenty of tracking numbers that just take me to a page that says “label created - USPS/UPS/FedEx awaiting item” until the carrier receives it. Some won’t give me tracking until it’s been picked up by the carrier, because there’s no point tracking an item that hasn’t shipped, but the number still exists.