Unexpected onAppear called when switching out from a NavigationView

ContentView.swift

import SwiftUI

/*
 Navigating through to LoggedInView prints the following:
 
 WelcomeView
 LogInFormView
 LoggedInView
 WelcomeView -> Why is this view's onAppear called when it's not on screen??
 
 */

struct ContentView: View {
  @State var isLoggedIn = false

  var body: some View {
    if isLoggedIn {
      LoggedInView(logOut: { isLoggedIn = false })
    } else {
      NavigationView {
        WelcomeView(logIn: { isLoggedIn = true })
      }
    }
  }
}

struct WelcomeView: View {
  var logIn: () -> Void

  var body: some View {
    NavigationLink(destination: LogInFormView(logIn: logIn), label: { Text("Go to form") })
      .onAppear { print("\(Self.self)") }
  }
}

struct LogInFormView: View {
  var logIn: () -> Void

  var body: some View {
    Button("Log in", action: logIn)
      .onAppear { print("\(Self.self)") }
  }
}

struct LoggedInView: View {
  var logOut: () -> Void

  var body: some View {
    Button("Log out", action: logOut)
      .onAppear { print("\(Self.self)") }
  }
}