I think we need to move away from drone ownership as a thing. Unlike a car which has a title, the drone is personal property and there is no legal ownership established. Basically if you have the drone in your possession, you are probably the owner unless you obtained it illegally. There's no reliable list of serial numbers vs email addresses and there's no official process other than effect a transfer between parties. If a person buys the drone with their details and they give it away to a relative, the seller has no way of knowing anything about ownership.
It is true that Amazon will buy, for example, 25000 DJI Mini drones from Amazon. They will arrive and go to an Amazon warehouse where they will be sold one at a time to customers. DJI knows which drones they shipped to the Amazon warehouse but that's probably the end of it...until they hear back from the customer with a warranty request or a Care Refresh claim or a repair order. However, if Eastern Nebraska Drone Center wants to sells DJI Mini drones thru Amazon and they obtain 200 from DJI or have them shipped to the Amazon warehouse to be fulfilled to buyers then that warehouse may have 25,200 drones in stock. The big computer will take care of everything but you can see how DJI doesn't "own" all the inventory in their warehouse. I'm not saying there isn't any sort of physically separation or other identifying traits because I just don't know for sure but if it's the same UPC and it comes from the same factory in China, there's no reason not to co-mingle the inventory.
The bottom lines is other than the example given in post #23, there's no reason for a buyer to be overly concerned about anything the ship from Amazon and for sure, there is no valid reason to trying to establish "ownership" because it just can't be done.
It is absolutely true there are thieves in this world who will receive a locked drone and then buy a good drone from Amazon and return the locked one in its place. That's the oldest trick in the book and it didn't start (and it won't end) with drones. But there a remedy in place to handle that type of fraud as long as everyone is cooperating and knowledgeable.