Just a small correction, 5200kgs of juice on a B777-300 ER equates to about 43 minutes endurance with flaps 1.
From my armchair, it looks more like a communication problem with the Chinese f/o saying stuff to ATC which the Korean skipper probably knew nothing about. There are a lot of smart arse RHSeaters in all airlines, especially those who work in their national carriers using their own mother tongue in communications with ATC. ATC ZSSS should have just vector him away.
This incident will probably scare off a lot of Korean pilots from applying to Juneyao, Air China Cargo, Yangtze.