I don’t know because if Uther became the beings who designate then going to the maw would be correct but I probably missed something.
And it’s not fair to kill Sylvanas in an Arthas redemption arc since he already killed her and started this whole thing with making her darker than she would have been destined for, much like his own story.
I think they both deserve arcs because both Arthas and Sylvanas, their hated forms, were created.