An anonymous author ("Fred") posted a comment in Harvey Organ's blog answering my question on the delivery process:
Metal moved into a COMEX approved warehouse initially enters as "eligible" to be used for contract settlement. That's the term COMEX uses. Why Harvey uses "dealer" and "customer" is beyond me. If the holder of the metal sells it to a miner or industrial user or investor directly, there is no need for it to be assigned a COMEX warehouse receipt number and the metal can just sit in the account of the owner for as long as desired.
Once metal is "registered", that means it has been assigned a receipt number and that receipt can be delivered against a COMEX contract.
"Delivery" of a COMEX contract entails nothing more than the moving of a receipt from one account to another. It DOES NOT mean metal leaving the warehouse unless the holder of the receipt wants to withdraw metal. Withdrawl of metal is not part of the COMEX delivery process. It's a separate transaction between the owner of the metal and the depository.
So warehouse movements and delivery notices are much less connected than Harvey would have you believe.