[Mistake]: React 19 says that startTransition callback must be synchronous. It is not true.  #7027

Summary

Since this change: https://github.com/facebook/react/blob/main/CHANGELOG-canary.md#october-5-2023-1830-canary-546178f91-20231005

The line

The function you pass to startTransition must be synchronous. React immediately executes this function, marking all state updates that happen while it executes as Transitions. If you try to perform more state updates later (for example, in a timeout), they won’t be marked as Transitions.

is no longer true.

Page

https://19.react.dev/reference/react/useTransition

Details

No response