NSManagedObject ignores return value of automaticallyNotifiesObserversForKey: ands KVO notifications

Question

I noticed that changing a managed property in a subclass of NSManagedObject sends KVO notifications, even if I overwrite the automaticallyNotifiesObserversForKey: to return NO.

+(BOOL)automaticallyNotifiesObserversForKey:(NSString *)key{
    return NO;
}

Is this the expected behaviour?

If I change a non-managed property, everything works as expected (no notification is sent).

What's going on and why the difference between managed and non-managed properties?