. The reason is that
the engines on the 747 are deemed to have a very strong windmill, so even if "dead" they are able to turn freely
to generate electricity and of course there are 4 of them, so losing them all is very unlikely. So it was decided on
the 747 to allow the engines to windmill for electricity, or to have one of the running engines support power.
What is this, model aircraft design? Who in United is involved?
That site is full of half truths. When an engine is windmilling, it will produce hydraulic pressure, and power the dedicated generator for the FADEC. It will not produce electricity from the IDG.
I hope you are not a real pilot reading this!