There's a big literature on this in Chinese history -- many arguments concentrate on economics and labor specifically (to crudely sum it up, there was always lots of cheap labor available, and little incentive to invest the capital to develop and build expensive machinery so as to replace it). There are cultural and intellectual arguments too.

But this piece is totally wrongheaded in that it supposes that South China is China. For most of Chinese history, North China has been politically, socially, and culturally dominant (and not infrequently economically dominant too). It's too cold and arid to grow rice, and thus grows wheat and other grains. (This is why the cuisine is dominated by bready dumplings, e.g. mantou) Some of the author's arguments about rivers could apply to the Huang He (the Yellow River), too, but it has historically been much more central to Chinese civilization than the Yangzi ("Yangtze", or Chang Jiang - lit. "long river").