It isn't a KVO
issue, it's an issue with what you're trying to do because the FRC requires that the sort can be applied to the underlying SQLite store. In other words, you can only filter and sort on non-transient attributes. You will need to make the attribute non-transient so that it's value is saved into the store and available to SQLite.
For the FRC, only the section name key path attribute can be transient.