Weird SwiftUI two-column NavigationView behavior

TwoColumnNavigation.swift

// 1. Run on iPad simulator in landscape (= two-column navigation view).
// 2. Drill down to level 3
// 3. Observe console output.
//
// Result with .navigationViewStyle(.stack) (as expected):
//   Level 1: drilledDown=false
//   Level 1: drilledDown=true
//   Level 2: drilledDown=false
//   Level 2: drilledDown=true
//   Level 3: drilledDown=false
//
// Result with .navigationViewStyle(.columns):
//   Level 1: drilledDown=false
//   Level 1: drilledDown=true
//   Level 2: drilledDown=false
//   Level 2: drilledDown=true
//   Level 3: drilledDown=false
// → Level 1: drilledDown=false
//
// Note the last line!

import SwiftUI

struct ContentView: View {
  var body: some View {
    NavigationView {
      DetailView(level: 1)
    }
    .navigationViewStyle(.stack)
//    .navigationViewStyle(.columns)
  }
}

struct DetailView: View {
  let level: Int
  @State var drilledDown: Bool = false

  var body: some View {
    let _ = print("Level \(level): drilledDown=\(drilledDown)")
    List {
      NavigationLink(isActive: $drilledDown) {
        DetailView(level: level + 1)
      } label: {
        HStack {
          if drilledDown {
            Image(systemName: "checkmark")
          }
          Text("Drill Down")
        }
      }
    }
    .navigationTitle("Level \(level)")
  }
}

struct ContentView_Previews: PreviewProvider {
  static var previews: some View {
    ContentView()
  }
}