As for this part of the storyline, Fang Zheng remembered it very clearly.
Because Akemi Homura had told him, in her countless loops, there were a few "events" that would never change.
For instance, QB is always tirelessly encouraging Madoka to sign the contract, and then there's the appearance of Witch's Night, followed by Miki Sayaka's darkening.
According to Akemi Homura, if Miki Sayaka didn't sign the contract to become a Magical Girl, it would be fine, but once she did, she would inevitably darken, warp, and become a Witch, only to die!
No exceptions!!
