SwiftUI: unexpected behavior with two List side by side and a NavigationView

I have a screen with two List side by side, inside a NavigationView. The layout is rendered correctly, and I can independently scroll both lists. The problem is that, when I scroll the first list, it goes behind the navigation bar without triggering the effect of applying a background color to it. Here's a gif showing what's going on:

And this is the code I'm using for this view:

struct ContentView: View {

    var body: some View {
        NavigationView {
            HStack(spacing: 0) {
                List {
                    Section(header: Text("Header left")) {
                        ForEach(0..<600) { integer in
                            Text("\(integer)")
                        }
                    }
                }
                .listStyle(InsetGroupedListStyle())
                .frame(minWidth: 0, maxWidth: .infinity)

                List {
                    Section(header: Text("Header right")) {
                        ForEach(0..<400) { integer in
                            Text("\(integer)")
                        }
                    }
                }
                .listStyle(InsetGroupedListStyle())
                .frame(minWidth: 0, maxWidth: .infinity)
            }
            .navigationTitle("Example")
        }
        .navigationViewStyle(StackNavigationViewStyle())
    }

}

Would this be a SwiftUI bug? If not, how can I make the first list correctly interact with the navigation bar when scrolling?