Last FlatList item component re-mounted when adding new elements at the beginning of the list

Description

Each time a new component is added at the beginning or in the middle of the list, the last component (the one that was added first) re-mounts. I've noticed that when a new component is added to the list, a spacer component is created and it always replaces last component in that list, even if new components are added at the beginning or in the middle of the list. This makes last item to completely re-mount. This problem only occurs when the initialNumToRender is exceeded.

Steps to reproduce

1. Run repro from linked snack.
2. Press add button multiple times (at least 4).
3. You will see in the terminal that after reaching initialNumToRender last item is unmounted.

React Native Version

0.74.1

Affected Platforms

Runtime - Android, Runtime - iOS

Output of npx react-native info

System:
  OS: macOS 14.4.1
  CPU: (11) arm64 Apple M3 Pro
  Memory: 110.58 MB / 18.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 21.7.3
    path: /opt/homebrew/bin/node
  Yarn:
    version: 4.1.1
    path: /opt/homebrew/bin/yarn
  npm:
    version: 10.5.0
    path: /opt/homebrew/bin/npm
  Watchman:
    version: 2024.04.08.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.14.3
    path: /opt/homebrew/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 23.5
      - iOS 17.5
      - macOS 14.5
      - tvOS 17.5
      - visionOS 1.2
      - watchOS 10.5
  Android SDK:
    API Levels:
      - "31"
      - "34"
    Build Tools:
      - 30.0.3
      - 33.0.1
      - 34.0.0
    System Images:
      - android-34 | Google APIs ARM 64 v8a
      - android-TiramisuPrivacySandbox | Google Play ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2023.2 AI-232.10300.40.2321.11668458
  Xcode:
    version: 15.4/15F31d
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.10
    path: /usr/bin/javac
  Ruby:
    version: 2.6.10
    path: /usr/bin/ruby
npmPackages:
  "@react-native-community/cli": Not Found
  react:
    installed: 18.2.0
    wanted: 18.2.0
  react-native:
    installed: 0.74.0
    wanted: 0.74.0
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: false
iOS:
  hermesEnabled: true
  newArchEnabled: false

Stacktrace or Logs

-

Reproducer

https://snack.expo.dev/@exploifswm/flat-list-item-re-mount

Screenshots and Videos

No response

まず、リンクされた Expo Snack の再現コードを React Native 0.74.1 で実行し、リストが initialNumToRender を超えた後の FlatList の動作を調べます。Android と iOS の両方で、先頭または中央に新しい要素を挿入したときに、どのリスト項目が unmounted されるかを追跡します。新しい要素を追加しても既存の最後の項目が remount されなくなれば完了です。