As one of the engines was thought to have been damaged and on fire, it is possible that fuel dump was carried out on the other side only. Perhaps, there could be a matching image found in the Indian sources.
It looks like the Aviation Herald list of known incidents is incomplete. The Air France incident appears a more likely candidate, given the fact that the Facebook thread is mostly in French.
The tail paint also is compatible with the Air France livery. I found another photo of this fuel dump: F-GITI by alexis boidron, on Flickr
Fuel dumps on aircraft like the 747-400 are generally done symmetrically, in that the drill is to set the fuel remaining value that you want and open both wing jettison valves. This initiates the pump sequence. You want the fuel out of the big centre wing tank first, followed by the fuel in the larger inboard wing tanks. The system will do this automatically.
Once the centre tank is empty and the system senses an imbalance between the two inboard tanks (main 2 and 3), it shuts down the pumps in the tank with the lower value until balance is restored.
I thought that this would be the answer here but the schematic reveals a fuel cross flow manifold in the system that should still have fuel coming out of both jettison valves in this situation. It is pictured just above the STAB tank.
So the only real answer here as far as I can see is that one of the jettison valves failed to open.
I agree, that seems to be the only plausible explanation. No matter what other valves or pumps operate it's all going to the Jettison/Fueling manifold. Then if either of the jettison nozzle valves are open it will come out. There's no other way of making it come out of just one side.