As long as human is involve in the process, that's always loopholes for the AD/SA to sell watches to the flippers.
The action of "flipping" is an arguable term like our political situation of "jumping ship", complicated and difficult to stop.
Maybe, there should be some contractual binded terms and conditions between the AD and buyer, i.e. if the buyer want to sell the watches in say within 3 years, the buyer must sell it back to the AD at certain agreed price. Else, the action will be deemed as "flipping", and their names will be blacklisted for life by the AD.