The second interpretation is that there aren't actually that many "Soul Destruction Mode" chapters, nor are there so many arenas with appropriate rules.
From beginning to end, the site of the Disciple War has always been within the same chapter, only the war zones varied.
Even, it's possible that the war zone has always been the same, only the disciples involved were unable to perceive it.
The master did not choose chapters according to the rules of the Disciple War, but instead, he established the rules of the Disciple War based on existing chapter modes!
He did not cooperate with the "Librarian," but rather he formed some kind of cooperation with the evil god within the chapter.
Between the two interpretations, Lin Xun was more inclined towards the second.
If the reality were like the first interpretation, it would be too despairing.