No, there is only one species of black walnut east of the Rockies. There is a separate, rare and threatened species in California, but it is a small, shrubby tree and only grows in very warm climates.

But, as you've found out, with any plant, there is genetic variability in the population, with some having better quality than others.

I guess that's why plant breeders throw out so many plants from each "growout" -- I guess it's not unusual, when breeding something like apples, to plant 1000 seedlings and discard all but 2 or 3 of them after they reach bearing age and the fruit can be evaluated.

Dennis
SE Michigan