FTA: “...which uses the fuel as a coolant to absorb heat from the JSF’s powerful subsystems...”
It’s not an engine issue per se...sounds more like it’s a systems cooling issue.
If the fuel is too hot, it can’t act effectively as a heat sink to draw off heat from the avionics packages.
Avionics do have to be kept cool. On the ground in warm climates that’s what you have Huffers, and APU’s (Aux Power Units) for, to keep cool air flowing until you get the engine up to provide bleed air for cooling. You get the cool bleed air from the intake side of the engine before it gets to the combustion chamber. This report still sounds like BS. Now if someone familiar with the design says that they designed it to use the fuel as a coolant and eliminated bleed air to increase performance, then I would say they did not think that through.
Using the fuel for additional coolant is one of those ideas that sounds really cool and innovative, until you think about it for a minute.