At one point in the not too distant past the "absinthe" in the US was basically grain alcohol with food coloring. This coincided w/ the surge of absinthe popula

At one point in the not too distant past the "absinthe" in the US was basically grain alcohol with food coloring. This coincided w/ the surge of absinthe popularity and led to people pointing fingers as to what was different, often the thujone level. This is no longer the case, nor did it have anything to do with thujone. As you note, spirits which are extremely herbal in nature are going to have natural variance between recipes as each vendor finds their own unique flavor (e.g. fernets)