SwiftUI view does not update when NSManagedObject is updated from CloudKit

Question

I have a SwiftUI app with CoreData+CloudKit integrated. My data model is as follows:

• MainElement <->> SubElement <-> SubElementMetadata
  Each MainElement has one or more SubElements and each SubElement has exactly one SubElementMetadata.

Now I have a SwiftUI view to display the list of SubElements of a MainElement:

struct SubElementListView: View {
    
    @ObservedObject private var mainElement: MainElement
    
    init(mainElement: MainElement) {
        self.mainElement = mainElement
    }
    
    var body: some View {
        List(mainElement.subElements, id: \.self.objectID) { subElement in
            VStack {
                Text(subElement.title)
                Text(subElement.elementMetadata.creationDateString)
            }
        }
    }
}

The Issue:

When I update creationDateString of a SubElement somewhere in my code, the view updates to reflect the change. If, however, a change arrives over CloudKit, the view does not update.
If I navigate out and back into the view, the new data is displayed, but not while I stay on this view.

Why is this? I am aware I can probably trigger an update manually (e.g. by listening to CloudKit notifications), but I would like to understand why it doesn't "just work" - which is what I would have expected since NSManagedObject is also an ObservableObject.