What's the deal?

[Thomas]

There are a host of varietal clones and many go by the name of the original. Cloning is a technique now used to create varieties that can withstand "un-natural" growing conditions, which is how Riesling, Chardonnay, Cabernet Franc, et al, can make it in the Finger Lakes region.

So, if Zinfandel and Primtivo are clones of the same grape, then they are--essentially--the same varietal.