"Isn't this this sort of social engineering that the Chinese government does, which our hacker spies are now admitting to?"
Yes, but as usual government are behind the times. This is no different from things companies have been doing for years. "Digital" departments seeking to build up Facebook friends, sales departments seeking to manipulate search engine rankings, or marketing departments seeking to buy their way up the "most respected brands" listings. Or HR departments seeking to pretend their company is a great place to work.
For many years government manipulated the media directly, in the UK it used to be "D notices". They probably used those to keep the press quiet about all the kiddy diddlers in the establishment, for example. Those don't work with the internet (although Cameron thinks the internet needs more government "help"), so the next best thing is to try and pretend that opposing opinion is less popular, or that your own views have some following. And in the Westminster/Washington/Moscow/Beijing bubble, fiddling the figures counts for success, whether that be output figures, unemployment, inflation, debt, or public opinion.