NavigationSplitView detail not updating

Question

Why does the button "Show second view" not work here?

struct ContentView: View {
    @State private var showSecondView = false
    
    var body: some View {
        NavigationSplitView {
            // Sidebar content irrelevant
        } detail: {
            if showSecondView {
                Text("Success!!").navigationTitle("Second View")
            } else {
                NavigationStack {
                    NavigationLink("Subview") {
                        Button("Show second view") {
                            showSecondView = true
                        }.navigationTitle("Subview of First View")
                    }.navigationTitle("First View")
                }
            }
        }
    }
}

When I remove NavigationStack it still does not work. When I remove NavigationSplitView or NavigationLink("Subview") it works. I am compiling for macOS 13.3.1 (a) with Xcode 14.3.