NavigationSplitView does not work on beta 1 or 2

This session provides sample code for NavigationSplitView to display a selected item in details view, and refers to the Backyard Birds sample app;

NavigationSplitView {
    List(backyardsData.backyards, selection: $selectedBackyard) { backyard in
        BackyardCell(backyard: backyard)
    }
    .listStyle(.carousel)
} detail: {
    if let selectedBackyard {
        BackyardView(backyard: selectedBackyard)
    } else {
        BackyardUnavailableView()
    }
}

However, the sample code does not work on watchOS 10 beta 1 or 2, and even the sample app Backyard Birds does not use this pattern in code (this links to Watch ContentView file on Apple's GitHub repo).

To make sure I wasn't crazy, I've tried to navigate to details view when the data set is:

• a @State var with array of items
• a class conforming to ObservableObject and holding a @Published array of items (similar to what Backyard Birds is doing)
• FetchedResults from CoreData

None of them do anything when a “cell” is tapped.

My conclusion is that it isn't yet implemented [right]. Has anyone else got it to work?