"The Forbidden Nun" Jonabel Marsha likely didn't expect that due to the presence of Observer No. 19, Su Lun would so quickly notice the imperceptible flaw in her time secret technique.
Since he hadn't died, Su Lun also had some speculations about the enemy's peculiar time ability.
For example, the time point of a later time reversal most probably couldn't cover the previous one.
Just now, Su Lun had relied on his super-strong neural response to pull on a thread to save his life the instant his heart was pierced.
If the opponent could cast spells without any restrictions, no matter what Su Lun did, the enemy could just reverse time to the instant when his heart was pierced again. Then the opponent could "second-guess" that he would use a thread to escape and would simply predetermine this outcome, cutting off this escape route as well.
Su Lun's fate would be sealed as death was inevitable.