People in Provincial City still don't quite grasp modern concepts; you mention things like pre-sale and mortgages, and ninety-nine percent of them just stare blankly. Buying a house is a big deal; your house isn't even constructed, I haven't seen what it looks like, and you want me to fork over the money? Who's the fool here, you or me?
For real estate developers to get their hands on land, dig a pit, and start collecting money, or even to rely on just a couple of blueprints to recoup a considerable amount of capital right after securing the land... to be honest, those in property development haven't even dreamt of such things yet.
Following this model, one can imagine just how much liquid capital real estate developers have. So now, property developers take one plot of land, develop it, have money in hand, and then gradually develop another plot. Hoarding land or buying it isn't common, and there really aren't many buyers.