The thread on bourbon values under $20 got me thinking that what distinguished the picks was they don't have a strong corn flavour. They might have a dash of it, but are not dominated by a corny taste. In some cases age alone takes care of it, e.g., in BT; in others it's just the way the whiskey is matured, mingled and selected.
In the 1800's, any bourbon 4-6 years old would have been regarded as fully aged, maybe even old. (VOB's name exists for a reason). At this age, you often get a little corn taste but sometimes almost none: Old Forester Signature is a good example of a fully matured bourbon yet which is not woody.
As I get on with bourbon, I find more and more I like the mid-age space. Four to eight years of barrel age seems generally right but always with exceptions. Like most I like a well-aged bourbon once in a while.
FC, an excellent value, leans a bit more to the corn than some others in those under $20 picks, or say EW Black or BIB, but I like a hint of corn in bourbon. If you take away all the corn and replace it with heavy sweet bourbon barrel flavors, I think something of the historical nature of the drink is taken away.
The trick is to get a full-tasting, soft, balanced bourbon at that age range. Many of the picks provide that and each bottle tends to be a little different at least in texture and mouthfeel (but often more). I like to vat to increase complexity and I mentioned a bourbon recently comprised of 4 and 6 year old bourbons with only a dash of EC 12 that was outstanding IMO.