ListStyle weirdness in iOS 15

iOS 15 has messed up the appearance of some of my lists. Try this code:

import SwiftUI

struct ContentView: View {

//    let arrayOfStuff = ["Horse","Cow","Screwdriver","Blender","Pyramid","Scotch Tape","Baseball card","CD","Checkbook","Fountain pen","Pin cushion","Couch","Potatos","Protractor"]

let arrayOfStuff = ["Horse","Cow","Screwdriver","Blender"]

@State var currentlySelectedItem = ""
    var body: some View {
        ZStack {
            Color(.red)
                .ignoresSafeArea()
            List {
                ForEach(arrayOfStuff, id: \.self){ item in
                    Text(item)
                        .onTapGesture {
                            currentlySelectedItem = item
                        }
                        .listRowBackground(currentlySelectedItem == item ? Color.gray : Color(UIColor.systemGroupedBackground))
                }
            }
//            .listStyle(GroupedListStyle())
            .listStyle(PlainListStyle())
            .frame(width: 500, height: 500, alignment: .leading)
        }
    }
}

When running with the plain list style, the area of the frame that doesn't include any rows becomes transparent. When running with the GroupedListStyle, the empty area stays white. That's the behavior I want, but I want the tighter margins of the plain list style. It was all working fine in iOS 14.