You got me all wrong Non-grapenut!
I've had excellent moonshine made in a copper still. The still allows you to separate undesirable flavors and alcohols. A good distiller using good ingredients can make better liquor than you'll find in a store. Unless you know somebody personally the good stuff will be hard to come across. Not many share with strangers for obvious reasons.
Also, all the big boys use copper. It neutralizes sulfur compounds giving a cleaner taste. Same reason winemakers sometimes use copper sulfate to clean up hydrogen sulfide gas. Back to jacking...
Freeze distilling, as when jacking cider, concentrates all the various alcohols and solvents that are in a fermented beverage. In order of pure boiling points: Acetone (nail polish remover), methanol, ethyl acetate, ethanol, 2 propanol (rubbing alcohol), 1 propanol, butanol, etc. There is no way to separate those out, so you end up drinking them in a now more concentrated form. Ethanol poisoning will get you long before the others if you drink too much, but it's a short road to a sore head. For what it's worth, apple has an inordinately high amount of methanol, as do pears. You'd be better off doing this with just about anything else, except oranges.
I've never had Calvados, Tooth. Had plenty of apple shine made from cider, though and the apple jack was nothing like it. The best I could describe the apple jack was dirty apples and gym socks. And the cider it was made from was excellent.