Flutter all widgets in drawer navigation get mounted on startup

It seems that all the Widgets in the DrawerNavigation seem to be mounted on start-up, this includes any child widgets too. dispose seems to be called only when restarting the app. I am assuming this is NOT the intended lifecycle of widgets. I would expect each Widget(Screen) to be mounted when navigating to it and unmounted when navigating away.

This is my HomeScreen where navigation is handled:

class HomeScreen extends StatefulWidget {
  const HomeScreen({Key? key}) : super(key: key);

  @override
  State<HomeScreen> createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  //! Default to tribe overview screen - 1 -, 0 is mail screen
  int _drawerNavIndex = 1;

  /// [setSelectedTab] will update the current screen based on the tapped option
  /// from [DrawerContentWidget]
  void setSelectedTab(index) {
    // if the [_drawerNavIndex] is not the same as [index] update it to [index]
    // value
    if (_drawerNavIndex != index) {
      setState(() {
        _drawerNavIndex = index;
      });
    }
  }

  /// [selectedTabContent] will return the screen selected from the
  /// [DrawerContentWidget] based on [_drawerNavIndex]
  Widget selectedTabContent() {
    List<Widget> pages = [
      // Tribe Screens
      const TribeMailScreen(),
      const TribeHomeScreen(),
      const TribeAdvisorScreen(),
      const ConstructionScreen()

      // Alliance
    ];
    return IndexedStack(
      index: _drawerNavIndex,
      children: pages,
    );
  }

  @override
  Widget build(BuildContext context) {
    TribeSummary tribe = Provider.of<TribeSummary>(context, listen: true);

    // If the tribe uid value is `placeHolderTribe` assume that there is no
    // existing or active tribe for this account
    if (tribe.uid == 'placeHolderTribe') {
      return Scaffold(
        /// TODO: create a proper drawer or appBar for the [StartTribeWidget]
        appBar: AppBar(
          title: const Text('A flutter app'),
        ),
        body: const StartTribeWidget(),
      );

      // If the tribe `uid` value is `placeHolderTribe` assume that an error
      // occurred while trying to get the tribe stream or while the tribe stream
      // is parsed to [TribeSummary], log should give more information
    } else if (tribe.uid == 'placeHolderErrorTribe') {
      // TODO: create a bettter error screen for this situation
      return const Center(
        child: Text('Unable to retrieve tribe data'),
      );
    }

    // This Scaffold wraps the entire app, anything here will be avilable
    // globally
    return Scaffold(
      // App Bar
      appBar: const AppBarContent(),

      // [DrawerContentWidget] holds all the drawer content, it requires
      // [setSelectedTab] function to handle the navigation between screens and
      // [selectedTabIndex] to highlight the selected tab
      drawer: DrawerContentWidget(
        setSelectedTab: setSelectedTab,
        selectedTabIndex: _drawerNavIndex,
      ),

      // Display the contents of the selected screen
      body: selectedTabContent(),

      // Reserved
      bottomNavigationBar: SizedBox(
          height: 50,
          child: Container(
            color: Colors.red[100],
            child: const Center(child: Text('Reserved space')),
          )),
    );
  }
}