Why is the .opacity AnyTransition is marked as nonisolated(unsafe)

Because of this, in Swift 6 mode, Xcode complains about the access, and ask me to use unsafe keyword.

To fix it, I need to do this:

Anyone can explain this abrupt nonisolated(unsafe) change?

Why is the .opacity AnyTransition is marked as nonisolated(unsafe)
 
 
Q