toolbarBackground Multiple tabItem settings with different backgrounds conflict.

import SwiftUI

struct MainScreen: View {
    var body: some View {
        TabView {
            Text("First")
                .tabItem {
                    Image(systemName: "map")
                    Text("First")
                }
                .toolbarBackground(.visible, for: .tabBar)
            
            
            List {
                ForEach(0..<5) { index in
                    Text("Item \(index + 1)")
                }
            }
            .tabItem {
                Image(systemName: "flag")
                Text("Second")
            }
            .toolbarBackground(.automatic, for: .tabBar)
        }
    }
}

struct MainScreen_Previews: PreviewProvider {
    static var previews: some View {
        MainScreen()
    }
}

Why the background of Second TabItem is not automatic? But it is affected by the configuration of First TabItem?