Wow, that's even worse then. Sooo - let's assume a standard grassland tile - yields from a Siheyuan in modern era: 2

3

3

4

4

(at most). Well, it's certainly not bad, but I just don't see how it is as powerful as you've described. By that time pastures, camps, mines, etc. get so many yields from techs, buildings, policies that they easily match with these numbers.
The only seriously strong thing I see here that has the potential to make China snowball early, is the culture that early on (I forgot which tech unlocks the Siheyuan, but I assume it's quite early). If that is removed, what's left? Science is really nice, but it has nowhere near the potential (especially with so many other science focused civs).
Anyways, that's just my 2cents. I seriously have to go give it a go, because I just honestly don't see the huge problem here (other than
maybe the early +2 culture from 1 tile, that can be spammed relatively easily).
Yes but they don't gain anything from each other, right? They need to be placed next to a city or next to two other, that's it. There is no synergy buff, like farms, Ekis, etc. Am I missing something?