Flutter RootRestorationScope not restoring last root

I was using this plugin https://pub.dev/packages/last_state, but when i update to flutter 1.22 a new feature came out RootRestorationScope that seems could replace that external plugin, but after testing it and following some tutos (tuto1, tuto2) i noticed that it restore the state but it does not restore the route ! am i missing something ? there is an example:

import 'package:flutter/material.dart';

void main() => runApp(
  RootRestorationScope( // Register a restoration scope for the entire app!
    restorationId: 'root',
    child: MyApp(),
  ),
);

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: DummyPage(),
    );
  }
}

class DummyPage extends StatelessWidget {
  static const route = "/intermediate";

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Another page'),
      ),
      body: RaisedButton(
        child: Text("Onwards"),
        onPressed: () {
          Navigator.of(context, rootNavigator: false).push(
            MaterialPageRoute<bool>(
              fullscreenDialog: true,
              builder: (BuildContext context) => HomePage(),
            ),
          );
        },
      ),
    );
  }
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

// Our state should be mixed-in with RestorationMixin
class _HomePageState extends State<HomePage> with RestorationMixin {

  // For each state, we need to use a restorable property
  final RestorableInt _index = RestorableInt(0);

  @override
  Widget build(BuildContext context) {
    return RestorationScope(
      restorationId: 'tess',
      child: Scaffold(
        body: Center(child: Text('Index is ${_index.value}')),
        bottomNavigationBar: BottomNavigationBar(
          currentIndex: _index.value,
          onTap: (i) => setState(() => _index.value = i),
          items: <BottomNavigationBarItem>[
            BottomNavigationBarItem(
                icon: Icon(Icons.home),
                label: 'Home'
            ),
            BottomNavigationBarItem(
                icon: Icon(Icons.notifications),
                label: 'Notifications'
            ),
            BottomNavigationBarItem(
                icon: Icon(Icons.settings),
                label: 'Settings'
            ),
          ],
        ),
      ),
    );
  }

  @override
  // The restoration bucket id for this page,
  // let's give it the name of our page!
  String get restorationId => 'home_page';

  @override
  void restoreState(RestorationBucket oldBucket, bool initialRestore) {
    // Register our property to be saved every time it changes,
    // and to be restored every time our app is killed by the OS!
    registerForRestoration(_index, 'nav_bar_index');
  }
}