Both cases have applied to me in recent times. The first point more so that the project scope changed, and a new structure was needed.
For a DB refactoring feature (… or data migration, whatever the best label is), if there’s any worry about data integrity, then just slap a massive warning and disclaimer on it.
The ACF admin experience involves things opening & closing, drag-and-drop, forms being filled, etc. The ability for user-created elements in that experience to be renameable would be perfectly natural and expected. Going against that is a fight you can never win.
