confused by center behavior.

center.dart

import 'package:flame/components.dart';
import 'package:flame/game.dart';
import 'package:flutter/material.dart';

class FooGame extends FlameGame {
  @override
  Future<void> onLoad() async {
    debugMode = true;
    var paint = Paint()..color = Colors.green;
    double rectSize = 50;

    var rect1 = RectangleComponent.square(
      size: rectSize,
      paint: paint,
      anchor: Anchor.center,
    );
    var rect2 = RectangleComponent.square(
      size: rectSize,
      paint: paint,
      anchor: Anchor.center,
    );
    var rect3 = RectangleComponent.square(
      size: rectSize,
      paint: paint,
      anchor: Anchor.center,
    );
    rect2.add(rect3);
    rect1.add(rect2);
    add(rect1);
    print("rect1.position: ${rect1.position}");
    print("rect2.position: ${rect2.position}");
    print("rect3.position: ${rect3.position}");
    double worldSize = 1500;
    var worldBounds = Rect.fromLTWH(-worldSize, -worldSize, 2 * worldSize, 2 * worldSize);
    camera.followComponent(rect1, worldBounds: worldBounds);
  }
}

class MyGame extends StatelessWidget {
  const MyGame({super.key});

  @override
  Widget build(BuildContext context) {
    return GameWidget(game: FooGame());
  }
}

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