Right AK. The first circuit introduced by Dr. Clark eliminated the need to do the tapping. I guess that they just were confused.
However, battery tapping can be helpful in destroying some of the more fragile infectious agents such as rhinovirus ( colds ), Adenovirus ( colds / flu ), and Influenza. None of these are proven, but there is plenty of anecdotal evidence.
If I had a viral infection such as Ebola and I had no better alternative, I would use battery tapping on 9 volt battery or even on a car battery, even if it only gave me an additional 1 percent to 5 percent advantage.