It's been mentioned that barrels at the upper levels of the rickhouse will go up in proof over time. So if it was entered at low proof and store at the top levels, it would go up in proof over time.
Now whether such a barrel would be much better than your average barrel? Good question.
It could also be that they entered a number of barrels at low proof (perhaps as low as 80) for use in mingling when making a batch. It could be used to help offset some of the lost proof from lower rick barrels, as well as adding a range of flavors from barrels on different levels leading to increased complexity and depth in a whiskey. Also, instead of adding flavorless water to reduce in proof (or adjust proof) you add flavorful whiskey, which it would seem to lead to a better product. Of course, a cheaper product can be had by adding water which would lighten the flavor.
That's a hypothesis, not a fact, btw.
Cheryl Lins - Proprietor and distiller, Delaware Phoenix Distillery, Walton, NY