It does bring up interesting questions. There's plenty of examples where giving up an obsession with hating someone is far from the same thing as forgiving them or caring for their well-being.
So, Sylvanas is in our clutches. Once we get the information extracted from her that we need to stop Zovaal,
what do we do with her?
1) Despite it justifiably sickening everyone in every faction, if Sylvanas, now merged in soul and seemingly capable of understanding the wrong in her actions, tried to fix them? And I'm not talking some last minute selfish sacrifice like she tried to do (and hilariously failed) by flipping off Zovaal, but actual, rough, long-term fixing. Would Tyrande let that happen?
2) If Thrall took it upon himself to honor their last bargain, the proof that "the Horde has changed", what would Tyrande's reaction be? I just picture him throwing a bag with Sylvanas's head in it on her lap and her barely reacting, just handwaving and saying "burn it."
Of those theoreticals I'd pick #2 myself.