The player is of course the only one who has real agency in the game and the game and it's characters react to the player's actions, so you can look up guides to plan out your companions' reactions. Taken to the extreme, you can save-scum, reload or use mods to alter the world to your liking.
Sure, if you put it like that yes, the decision-making of all video game characters is all smoke and mirrors. But I suspect people who'd like to see Wyll make his own decisions aren't planning to take a walkthrough and save-scum to make sure he makes the right decision; or if they do they still think the story would be better if he said it
I think, Mizora mentioned, that the physical changes can't be undone, so I don't think, a Divine Intervention can help. Maybe a True Ressurection
The line I remember is something like "some magic even I can't undo", which I interpreted to mean Mizora can't reverse it. I don't want to be one of those "BG3 doesn't exactly match my stack of D&D books and is therefore bad", but I figured either a god would be more powerful, and/or Wish would undo it. But that's just my own out-of-game theory that's as relevant to the game as imagining my custom characters' personality
