I agree that it's something of a cop-out, to spare Keith having to make that choice, and to likewise spare him having to live with its consequences. But I also think that narratively, it would have opened a whole bag of worms: the aftermath would have rattled on for ages, and would have opened the question of whether they would ever meet again after all the dust had settled, etc. These are obviously questions of great interest, to myself and others (*gestures at all the fix-it fic*), but it wouldn't have been in keeping with the prophecy trope she was writing, and it wouldn't have had the resonant finality of the ending she chose.

I feel very much the same way about Znvgynaq'f raq va Gur Qnex Zvyr -- to let him live out his confession and redemption would have been long and messy, very nearly another story unto itself. Instead, she chose to give it a decisive, tragic ending. Which is definitely a tool that exists if you want to make someone feel the full weight of their choices/dilemma, without the messiness of them actually having to live with said choices or dilemma.