The Bracelet can make souls switch back, but it's also possible they may not be switched back; after all, both souls must agree for it to work.
Xiaoyao chose not to switch back initially with the consent of the original self, but would Xiaoyao's original self agree?
The original self should be very comfortable in the modern world. Coming back might be a dead end; would she give up modern times to return here? It's really uncertain.
However, for Xiaoyao to stop suffering, she nevertheless mentioned that souls could be switched back, hoping even for the slightest chance.
"Xiaoyao, listen to me. When the Bracelet arrives, touch it with your hand, your soul will be absorbed into it. Inside, a small Fairy will be waiting for you. He's there for soul restoration, and at that time, he will transmit the other soul from the modern world."
