I've been eating peaches, nectarines, plums, and apricots since I was a kid and my uncle in the San Fernando Valley of L A (perfect growing conditions) had fruit trees in his backyard. So I know the best, sweetest stone fruit is tree-ripened. In general, commercial growers have to pick their fruit hard for storage, shipping, and eventual display. Under optimal growing conditions and with the right varieties some of this fruit will have developed enough sugar to still taste good, but obviously not all. Does this make sense?