They could learn from Allaria who taught them how to change back, there, it's all stupid but cmon like is this really that much of a problem when looking at the other plot holes, like bringing back a corpse turned to ash by dragons kind of a plot hole?
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Void elves that can only transform when out of combat back while still having voices in their heads telling them to kill everything is a pretty big difference.
I know that it was, but it still didn't stop the annoying demand, and Blizz having to say the same thing over and over and over, it will satisfy both sides.