The onAppear for the wrong tab is being executed

I was seeing some behavior I couldn't understand with onAppear and my tabs (Xcode 12 beta 3). I wrote a quick project with two tabs to test. Here's tab1 (tab2 is the same).

   var body: some View {
    NavigationView {
    Text("Tab1")
    }
    .onAppear() {
      let datefor = DateFormatter()
      datefor.timeStyle = .medium
      print("onAppear tab1 \(datefor.string(from: Date()))")
    }
    .onDisappear() {
      print("onDisappear tab1")
    }
  }

At app launch:
onAppear tab1 10:29:18 AM
onAppear tab2 10:29:18 AM

Touch tab2:
onDisappear tab1
onDisappear tab2
onAppear tab2 10:29:42 AM
onAppear tab1 10:29:42 AM

Now this is where it gets interesting. Touch tab1 and the wrong onAppear gets called:
onDisappear tab2
onAppear tab2 10:30:10 AM

Touch tab2 and the same thing happens:
onDisappear tab1
onAppear tab1 10:30:46 AM