Originally Posted by
Someone Somewhere
I haven't been able to find this explained anywhere.
My guess is that it's some kind of lockout where the engine will refuse to start if it's on the ground and believes it's unsafe to do so, potentially implying a maintenance reset. If you tried to start an engine with a genuinely stuck open fuel valve, you might get a fireball or a sudden acceleration up to maximum thrust, knocking the aircraft off any chocks or parking brakes.
787 Operators NEVER power down their aircraft fully because powering it up again is a VERY long and painful process. When the crew walk away from an aircraft it is on gound power with the IRS and batteries turned off. If all engine generators unexpectedly dropped off line after landing you have a pretty dead aircraft that you might as well walk away from. The engineers will be busy for quite a while
resuscitating it.