What hasn't been said is that from the distributor/producer point of view, it's a sale of a barrel's-worth of whiskey to a store or bar that perhaps, ordinarily, wouldn't buy that much of that particular brand. It also gives the retailer an incentive to promote it, maybe at a better price, certainly with a display, maybe with ad support. The dealer is more invested so they're more likely to suggest that bottle to their customers.
The samples presented are always selections that would be appropriate for that brand. In fact, the barrels that aren't selected for a retailer single barrel probably go into the next general bottling, so it's still Weller Special Reserve (or whatever) but it's that buyer's selection from a number of possibilities, typically three to five. If the buyer goes to Kentucky they may get to taste more, if they want to.
Most producers allow individuals to do this too. You wind up actually buying your barrel in bottles from a local retailer, to comply with all the laws. Many individuals and groups here on sb.com have done it.
Woodford Reserve does it a little differently. Since Woodford batches always include whiskey from both Woodford and Shively, you have to pick two barrels from the samples offered, which they mix together. You only have to buy the equivalent of one barrel, though you can buy the whole lot if you want to.
For retailers, BF is only offering Old Forester and double Oaked. Regular woodford blends are not part of the program now.