I don't know about Eastern China, but I was told first hand from a relative:

a) General lack of maintenance in all buildings. At the most basic level this includes keeping things clean, at a higher level fixing things when they break.

b) Air pollution causing external wear.

c) Individual was surprised when told a stadium was 6 years old. It looked decades old due to pollution and lack of maintenance. The locals were just going to build a new one to replace it.

I have lived in Shanghai for the past 3 years but I also lived here from 2001-2002. Back then, there were buildings constructed that were totally empty and it seemed ridiculous to think anyone would live in those distant undeveloped areas. Fast forward a decade and now Shanghai has 20 metro lines instead of two, with each metro station under a sprouting mini-city, complete with its own H&M, Burger King and Starbucks. It seems like the urban planners placed tem all perfectly close to each other, like settlements in Civ. The condos that stood empty 12 years ago are now at full capacity and people are moving even further out into the exurbs where more empty buildings await them. The energy and buzz in Shanghai is just as palpable as it was 12 years ago and although there are some ghost cities and failed projects across greater China, the megalopolises will easily compensate for them. The United States has its share of empty, abandoned cities (Detroit, anyone?) but when you visit San Francisco or Manhattan, you would not know it.

A lot of this opportunistic construction isn't done very well, and often its just a form of money laundering (build this, charge a lot, do a very crappy job, lots of pockets are padded). Many of these buildings will be torn down before they are ever used; every few months there is a scandal where this actually happens.

Are there any statistics of buildings collapsing? I've seen the "tipped over building" picture, and heard some other sketchy stories but its all anecdotal.

If statistics exist, I'm sure they are covered under the state secrets law.

The result you point to, in terms of taking up overdevelopment slack due to China's urbanization having a long way to go yet, may turn out to be true. But it's generous to say anyone anticipated that in building these white elephant projects.

China's economic growth will cover numerous sins. As will the oil boom in the US. But they're still sins.