This is sounding to me like the term 'Cask Strength' is like the saga Diageo had with Cardhu...There is obviously no true definition of the term.
I would have thought some legal eagles would have been onto this??
Maybe there needs to be a legal definition of the term "Cask Strength" - The %Alc/Vol of the spirit in a single cask that has not had any additional additives before bottling or in the case of a vatting, the quantity of barrels to be emptied into a vat and taking the %Alc/Vol on the whole vat, having no additional additives before bottling.
That's what I would determine Cask Strength to be...
Same would go for Bourbon and the term "Barrel Proof".