That choice appears only if you sided with demons, probably you only saw the siding with witches playthrough.
And really it makes sense, siding with demons without consequences? Nah-uh

I have saves for both witches and demons and on the demons I split another save there one for quarantine (you won't see Morwen and Idril due to the quarantine and hence why they said lose 2 harem members but you save most of the elves) and other to kill the elves (murdereeeeeeeer

) but you keep Morwen and Idril around. Maybe worth in Realm 4, maybe not.
Picture of the walkthrough part.
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