1. These are Urban Homes.
2. There are roughly 20M people jumping to new cities and Urban areas every year. For years China has keep a roughly two years buffer zone, I think the rate of new housing is the same and rate of people going into Urban has declined, so a slight increase in terms of buffer ( closer to three years now ).
3. Most of the "Ghost Cities" do get fill up quickly, once the policy are in place for their turn.
These so called Home vacancies and ticking time bomb has been cycling through media every year. And it isn't happening ( yet ). There are 500M+ still living in rural areas ( Yes I know the number is a little hard to believe ) At least another 300M to go from rural areas to Urban, with 200M likely not going to get their turn as they age.
So from that perspective ( As much as I hate to admit it ) China really is still a developing country.