Those decent looking clusters are being cut off just to reduce the overall crop load. If the overall crop load is too heavy, it will stress the vine and all the clusters may not fully ripen. I think most winemakers would agree their definition of ripeness is not just a measure of color & sugar content anymore. Many years ago, most grapes in the valley were deemed ready to harvest based solely on the % of sugar content. That is no longer the case. I venture to say that most grapes being harvested in the Napa Valley these days are picked when the winemaker is happy with the flavors of the grapes. This is winemaker directed harvesting. It can drive growers crazy when the grapes are at say, 24 or even 25% brix, but the winemaker says "They're not ready yet".
Several of the vineyards farmed by Piña Vineyard Management for delivery to Piña Napa Valley, will have less fruit dropped on the ground this year. That's the good news. The bad news is that the reason there will be less fruit dropped, is because there is less fruit on the vines than in past years. Vines that were pelted with rain while in their "bloom" stage have a poor fruit "set". For these vineyards, we're anticipating a light harvest this year. It's a gambling business. Always has been.