The Chinese government wants to use that electricity for something else.
Or they'd just rather sell the electricity (which is produced in the public sector) to groups doing things which they regard to be more important.
Regardless, whether this news is true appears to be
a tad more complicated than just "the Chinese government bans mining Bitcoin with state-generated electricity".
As it is, mining could become more difficult due to the difficulty of trading BTC on exchanges. The OTC market may have to grow to handle this demand.