Duo not having different z index with overlay arrangement view style

When using ArrangementView with the overlay style, the Duo simulator does not appear to return a distinct z-index environment value, though it correctly displays z-index 0 and 1 on other iPhone simulators.

I would like to use this value to determine whether the overlay is active. Currently, this does not seem possible.

Is this behavior intended, or is it a bug? If intended, what is the recommended approach to determine if the Duo is displaying the arranged view over another arranged view?

import SwiftUI

struct ContentView: View {
    var body: some View {
        ArrangementView {
            Controls()
        } secondary: {
            Player()
        }
        .arrangementViewStyle(.overlay)

    }
}

struct Controls: View {
    @Environment(\.overlayArrangementZIndex) var zIndex

    var body: some View {
        Text("Controls Z:\(zIndex)")
            .frame(maxWidth: .infinity, alignment: .leading)
    }
}

struct Player: View {
    @Environment(\.overlayArrangementZIndex) var zIndex

    var body: some View {
        Text("Player Z:\(zIndex)")
            .frame(maxWidth: .infinity, alignment: .trailing)
    }
}

#Preview {
    ContentView()
}