Clark, of course every soil is different and one must experiment and adapt to their own conditions. I was speaking generally about gardeners and a tendency I’ve often witnessed about them not trusting their native soil at all. This includes the common act of attempting to maintain an extremely high organic matter content.
As far as high levels of N depreciating fruit quality, this is not an open and shut case, and I’ve seen research that indicates little connection to brix and rate of nitrogen application. I believe, however, that this research is done in areas that can control water input. Excess water is the main culprit in creating bland fruit (and excessive vegetative vigor, for that matter) and I suspect combined with excess N the situation could be worse.
Application of quick release N in early spring will not affect the brix, but may affect the size of the fruit.
Olpea mentioned the controversy about mulching fruit trees, and I have often stated the potential of mulch changing the quality of the soil after many years of annual application and breakdown into humus.
After 10 years or so, mulched trees are likely to become excessively vigorous, but it is hard to know if this is because of higher N release or improved water retention. My hunch is that it has more to do with the latter. If you live in an area that seldom gets much rain from mid-summer on you would have little to worry about.