After three weeks in Germany, I have the conclusion that it depends. What beer is being brewed, on what system, and other factors. Helles, yeah LODO is great. A Dunkel, maybe not required.
I was at a brewpub that had copper vessels from what I could tell, pretty simple system. The Helles had an oxidized flavor, so there you go. The Mandarina Pils was good, I didn't detect that flavor. The export Dunkel was super, full of yummy Mailliard products.
Even if the Helles seemed oxidized, you'd have to do a lot of work to know if it was connected to the copper. And why wouldn't it affect the other styles? Dunno, but it seems like circumstantial evidence.
Exactly, no argument. Copper, lots of splashing, do they mix the grist and liquor and drop from the top? Was the Helles old? I need to travel more and take more tours. ;-)
I have got that flavor before, at a larger brewery in the south of Bavaria. We went there for the view. Didn't see the brew house.