There is nothing strange about this. Depending on flight conditions or other restrictions, various services on flights have been disabled before.
- Meal service is stopped if the flight is going through turbulent weather.
- People are restricted to move around the cabin during normal flight.
- Cabin lights may be turned on during night time flights.
- The ICE (information, communication, entertainment) systems may be switched off.
It depends on what the crew feel is impacting the safety of the flight.
Once a colleague of mine was asked to turn off his laptop while the plane was sitting at the gate, with the engines turned off by the crew. He was as baffled as I am because normally in this scenario you are allowed to use electronics and radios.
However, he was asked to do so by the crew on the instructions of the captain.
Specifically for the use of mobile phones and wifi, this depends on the aircraft being flown. On Emirates, for example, the system is available on all their A380 aircraft, but only some of the 777-300s because these are the older aircraft in their fleet.
I am not aware of any restrictions specific to China regarding mobile use on commercial flights; but as a general rule you are only allowed to use the mobile phone if the crew allows you to do so.