I am calling BS on this report. If its liquid fuel and can be dumped into the combustion chamber, it should work just fine in a jet engine. F35 engine may be new hi-tech, but its still a jet engine.
The interesting thing is that all the tactical jets I have flown have had an oil/fuel heat exchanger to preheat the fuel and cool the oil.
The problem isn't in burning the fuel for propulsion - it's that the plane's systems which generate waste heat utilize the fuel supply like a heat sink. Having the fuel "pre-heated" causes electronic problems.
It is not the temperature of the fuel entering the engine. The fuel is used to cool the electronics.