250m is the limit for strict regulation. Newer buildings tend to be around 100m.

I would imagine that has more to do with curbing local officials’ habits of encouraging land speculation to plump up their budgets. The central government is trying to have its cake and eat it too when it comes to property that needs to rise in value to boost wealth but also not become totally unaffordable for first time buyers, and overheating the market doesn’t help with the latter.