Actually, the retailers make a lot of these assortment requests, in conjunction with Hasbro. After all, it's about getting wallets in their stores.
Sometimes though, an exclusive has a sell-through window where it is exclusive to a specific retailer for a period of time, and then gets a secondary wider release through other retailers. Occasionally, when that happens, the figure is slighty different ( running-change paint apps etc) to distinguish it from the exclusive in a minor way.
The key thing to remember is that retailer exclusives HELP the brand because the retailer bears the costs of any new tooling, thus adding to the tooling library Hasbro has. That means that you WILL likely see that given figure ( or at least parts of said figure) again at some point.