Precondition - Implied Attributes
Accepted answer
You are correct about your doubt. Usually a precondition is called when the work item is saved.
However, there are some "Preconditons" that are actually "called" before the save (and during the save).
All the "Required Properties" are "called" by the work item UI when the UI opens the work item to be able to show the decorations. What happens is that the UI reads the precondition configuration and calculates the required attributes for the decoration. I would assume the UI does something similar with the Implied Attributes, reads the configuration information for the Implied Attributes and acts on it.
Other than the "Required Attributes" I would assume the Implied attributes precondition is not really called on save. It might be just a placeholder to allow the configuration and to provide the aspect editors. You would have to look into the RTC SDK to be sure.