I was reading this, as well. The language seems very straight-forward, but the content does not seem accurate. The best teas in Japan come from good, honest farmers throughout Japan and there can be no relationship between region and quality drawn. My information comes from years of visiting and living on tea farms throughout Japan. The people who actually grow the tea are not paid an especially high wage, more often they are gouged by wholesalers who make the bulk of the money in the industry by collecting lower quality teas and blending them with low-balled, high quality teas to produce blends that are just barely palatable. The info on gyokuro and other teas is also only marginally accurate, so take it all with a grain of salt. A good overview, but confuses history with fact and is lacking the finer points of Japanese tea.
Large tea gardens can be found throughout Japan, mostly in the wel-know growing regions such as Kyushu, Shizuoka, Kyoto, Aichi, etc. Typically, the larger the tea garden, the lower the quality. A large tea garden requires more machine processing which can contaminate and damage the leaves. I have looked at google maps to locate larger tea fields in Shizuoka. You should try this out, it is very interesting.