I don't know, Rahsaan. I haven't (yet) been around for centuries. I am not yet, though I sometimes feel so, an Ancient of Days.
Seriously, I don't think the founders really thought all that much about the aspects of introducing daikon radishes as a foreign plant. I believe they were more focused, at the time, on which plants and insects and microbes they could use to effectively achieve what they needed in the vineyards. But I don't know: maybe it was a consideration. I'll attempt to find out.
What I do know, though, is that the biodynamic aspect is a steadily evolving situation, with essential learnings going on constantly. It is largely, now, accretive, in that modifications and adjustments, based on what actually happens in the vineyards (action/reaction; cause/perceived effect; idea/application) causes slow but noticeable change in what we do, and how we do what we do.
And careful, considerate thought goes into what is done. So there is a definite "first, do no harm" attitude, coupled with "no need for hurry; let's think it through first".
We do, however, use 50 or so cover crops. And I honestly don't know how many are "natural" to the specific area, or how many are "imported"
As to the skepticism of Italian-to-America grape varieties, I have to think what you are referring to there is a rather healthy (although admitedly laden with bureaucratic bungling and roadblocks) fear of viruses and diseases that may be imported along with the cuttings. Of course, there's reasonable prudence and blockades, and the two are very different. Again, I honestly don't know the whys and wherefores of that issue.
Another aspect of that ranch/vineyard is the constancy of applying natural methods to farming the grapes as opposed to using methods in the winery that would not be considered "natural-kosher" by purists from another camp. In other words, we don't assiduously avoid sulfites; neither are we cavalier about the use of same.
Case in point: the US threshold for "Organic Wine" in the US is 10ppm sulfites, which must be naturally occuring, never added. In the EU, it's 100ppm. As I said, we don't avoid sulfites, and we do allow them, but our standard sulfite level on average is 25--45ppm (varies according to variety and weather). We could easily go the "natural" route and avoid sulfites altogether---but both the vineyard manager and the winemaker agree that is not the kind of wine they wish to make. So we end up being dismissed as 'tree hugger organics" on one side, while the fanatics on the other side dismiss us for not following their holy path. *wink* We just think we're doing what feels right for us.
Bottom line: I'm really proud to be associated with the farmers and winemakers at McNab. I appreciate what they do, and what they are trying to achieve. And it's inspiring to me to have this vision of Dave striding through the vineyards in his never ending quest to grow the best vines, and produce the best grapes, that he can.