Prevent children from rebuilding in SliverList

Minimum example:

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
        title: 'Welcome to Flutter',
        home: Scaffold(
          body: CustomScrollView(
            slivers: [Example()],
          ),
        ));
  }
}

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

  @override
  State<Example> createState() => ExampleState();
}

class ExampleState extends State<Example> with AutomaticKeepAliveClientMixin {
  @override
  Widget build(BuildContext context) {
    super.build(context);
    return SliverList(
        delegate: SliverChildListDelegate(const <Widget>[
      SizedBox(
        height: 1400,
      ),
      CheckboxWidget()
    ], addAutomaticKeepAlives: true));
  }

  @override
  bool get wantKeepAlive => true;
}

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

  @override
  State<CheckboxWidget> createState() => _CheckboxWidgetState();
}

class _CheckboxWidgetState extends State<CheckboxWidget> {
  late bool _personalData = false;
  @override
  Widget build(BuildContext context) {
    return Checkbox(
      checkColor: Colors.black,
      onChanged: (bool? value) {
        setState(() {
          _personalData = value!;
        });
      },
      value: _personalData,
    );
  }
}

If you click the checkbox, then scroll out of view and then back in to view.. The box becomes unchecked. This is because the widget rebuilds...setting the _personalData to false. I would of thought addAutomaticKeepAlives would prevent the widget rebuilding and keep the state of the checkbox. How do I prevent CheckboxWidget from rebuilding?