Pan gesture localPosition bug?

main.dart

// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

// 1. Open the console so you can see the prints.
// 2. Scroll to the bottom of the red/blue container and tap.
//    The location of the tap is logged.
//    Notice that the local dy includes the scrolling and global does not.
// 3. Scroll back up to the top and start dragging.
//    The location of the drag is continuously logged.
//    After 2 seconds, the scroll position jump to the bottom.
// Expected: The localPosition includes the scroll.
// Actual: The localPosition is the same as if the scroll didn't happen.

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  final String title;

  const MyHomePage({
    Key? key,
    required this.title,
  }) : super(key: key);

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final ScrollController _scrollController = ScrollController();
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SingleChildScrollView(
        controller: _scrollController,
        child: GestureDetector(
          onTapDown: (TapDownDetails details) {
            print('tapped at ${details.localPosition}, ${details.globalPosition}');
          },
          onPanStart: (DragStartDetails details) {
            Future<void>.delayed(const Duration(seconds: 2)).then((_) {
              _scrollController.jumpTo(1200.0);
            });
          },
          onPanUpdate: (DragUpdateDetails details) {
            print('pan update at ${details.localPosition}, ${details.globalPosition}');
          },
          child: Container(
            width: 200.0,
            height: 2000.0,
            decoration: const BoxDecoration(
              gradient: LinearGradient(
                begin: Alignment.topCenter,
                end: Alignment.bottomCenter,
                colors: <Color>[
                  Colors.red,
                  Colors.blue,
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }
}