My understanding of single barrel bourbon goes something like this (please correct me if I'm wrong): Take a brand like Four Roses for instance. The distillers taste barrels and when they find a particularly good Barrel they pull it away from the rest and bottle it as single barrel. The non-single barrel bourbon will be made from combining many barrels to balance differences in taste.
Okay, now to my question - several brands are only available as single barrel. Specifically, I refer to Blantons and Rock Hill Farms. If barrels are not selected to be single barrel, then what bourbon do those barrels become? If every barrel becomes single barrel bourbon, doesn't that defy the whole point of single barrel bourbon?