Those people reporting on Ghost cities either have no idea what they are talking about and/or have ulterior motives in making such a big deal of such sites.
I don't have up to date statistics, but urbanisation in China is currently around 50%.
That's 650 million people, the vast majority of whom moved from the countryside to the cities, without counting migrant workers,
Expansions of exisiting cities could only accommodate so many so fast, in many instances, entire new towns and cities were created where once there was only farmland or wilderness.
This isn't all that unprecedented. Many nations have built their capitals from scratch, most recently Astana in Kazakhstan, with other famous examples include Brazilia in Brazil, Abuja in Nigeria. And these are just famous capitals.
Designing and building a new city from scratch has many distinct advantages compared to urban sprawl.
When a new city has just been built, of course it takes time to populate it. Jumping in and taking a bunch of photographs of newly finished, or area still under construction and marvelling at the lack of residents is so stupid, its akin to standing out in the rain and being surprised one gets wet.
The only appropriate response to such none sense is, "Duh! What did you expect?!"
A newly built city still standing empty 5, 10 years down the line would merit some reporting, but either most reporters lack the patients to wait so long, or far more likely, none of the gleefully named "ghost cities" would still qualify by that measurement, and the reports know that full well. So they rush in, often before construction had even finished, so they can take some pictures of empty buildings and declare another city a "ghost city" to appease their editors and hope to get a raise or promotion.
Western reporting on China is backend driven, where editors in London and Washington decide what they want to report and they take care in only sending the kind of people they know who would only focus on such stories and not 'go native' and, god forbid, file a positive story about China.