The good thing about using bottle juice is it already has asorbic acid in it, it's clear, and already aged a few months. So there is no need to add acid blend, pectic enzyme, or water. That means you don't have to boil it. Active fermentation should also be in an open pail as to allow unpleasant gases to escape. Letting the ferment run dry also introduces unpleasant taste that takes a long time to settle out. I guess when it all adds up with the recipe on Jack's site, it would take months to get it all back out.
Here is kinda how I look at it. The juice taste good to start. Fermentation produces alcohol and CO2. If it is properly degased, then pretty much any other off flavors that are left is from an uncontrolled production of byproducts which probably could have been avoided or at least reduced in the beginning.
Aging should be used for building a complexity of flavors and aromas but it seems like it is abused and only used for detoxification.