“You guys...” I make an attempt to use my head “... Do something that differs from the game, don’t you? Act and move everything in such a way that it doesn't match in the game?”
Only this answer can explain why the 'future' Salzaal saw is not the same as the present, and why the 'route,' which the wizard acknowledged everything, could not answer the true meaning of Arthur's letter.
Since the letter did not appear in the game or anime.
They ruined the play and did something that neither the game nor the anime permitted so severely that the future line was changed from now on, without knowing what will happen next…on purpose.
“That’s… That power… That knowledge...” I sigh, “It’s… bloody cheat, ever.”
The wizard says nothing else and the prince, who has remained silent for so long, places the teacup on a tile saucer. “So what?”
“Do you regret it?” As if I have not already caught up with him. “You don’t feel sorry at all?”