Way I see it:
I didn’t really suffer, because I’m just my continuity and that’s been erased. Knowledge of that erasure is itself a trauma, but in this case it’s one I consent to, so OK.
HOWEVER
A temporary* but fully sentient person was made to feel torturous pain and anguish, and then erased from existence*. For my and the doctors’ convenience. And I don’t consider that ethical. It wouldn’t be ethical if we created a temporary clone of me, with my memories, to suffer my pain with some sort of pain-transfer machine, and then we destroyed it, would it? Why is it ethical if the “clone” is in the same body?