I do agree with this though, angels appear to have free will. While "free will" is a weird and nebulous concept, surely beings without free will can't rebel. Like, by definition.
They can definitely be forced to abandon their positions of authority and whatnot, though. Go through all the motions of rebellion even if their will is set against it.*
Not really sure you can make the argument they couldn't have been forced to rebel outright as well, either... that (unfortunate) bit of retconning with the pharaoh paints the christian god as something entirely willing to strip something of its free will and screw with its head when the godcritter feels like there's a need. It may have been that the angels had free will, did not want to rebel, and was not given a choice. Or that they left heaven on god's command, or any number of things along those lines.
And yeah, the whole teaching/testing/responsibility thing kinda' falls apart in... quite a great number of situations. At least unless reincarnation is actually a thing (which, to be fair, some christian denominations hold to, to various degrees) -- soul can't exactly pick up much in the way of lesson from dying in utero, or starving before they can walk, or so on. Plus the thing's own actions flies in the face of that pretty hard -- there's not exactly a lesson to be learned from getting genocided, having your children murdered, your pregnant wives ripped apart, etc., etc., etc. If th'thing's intent is teaching it's really gorram
bad at it. Either that or the people that wrote the text
really screwed up the transcription, heh.
... it'd make a sort of sense that instead of cruel, the thing's just incredibly
incompetent, though. Like, all powerful, all knowing, all good, but... kind of stupid (to the point of not figuring out how to use that omnipotence to fix the problem), and not really that good at using the tools available. Would explain a hell of a lot. Would also kinda' slot in with how we're really bad at dealing with information overload -- maybe we
were substantially made in its image, and it's basically spent the last ever being mostly crippled by the omniscience. Less cruelty, more flailing migraine seizure.
*E: Well, set against it or nonexistent. As always, it's possible the people writing the text misinterpreted what happened, and saw rebellion or abandonment where there was only obedience.