You are correct, it is the cultivars that makes kava so exciting and it is the Pacific people that have grown kava for so long that made these cultivars through selective cultivation, they weeded out the wild kava (Piper Witchmanii) Spelling??? and they kind of created the noble varieties of kava that the world likes to drink, the wild or tuday kava is not used for drinking, only for medicine and even then very rarely.
It is interesting to note that Dr. Lebot did some genetic research on kava throughout the Pacific, even here in Hawaii and it shows that they all came from Vanuatu, they have the same genetic markers, so Dr. Lebot postulates that all the kava came from Vanuatu at one time or another.
And in Hawaiian literature it talks about a kava called "Mokihana" we have yet to find that kava, i would love to, the way it is described it sounds like it would be a good one. Aloha.
Chris