I'm not sure I believe the claims of exclusivity, but it may be true. "WOW" is a rebranded "Five Star" or maybe "5 Star." I'm going from memory, here, and although kava has improved my recall abilities, I am in my 90's.
Assuming Nakamal@Home is telling the truth, the competing varieties are all a little different, but in the same catagory: Koniak from Bula Kava House and Special Reserve from Kava Kauai. These are highly processed Vanuatu kavas. They are powerful because the signal-to-noise ratio is highly improved. Most of the inactive is removed, leaving with a much smoother, much lighter, and more psychoactive drink.
These won't kill you. The "bad stuff' is, arguably, in the stuff removed from these blends - the bark.