TextInput onChangeText is firing at wrong time when type with Chinese input keyboard in iOS

Description

TextInput onChangeText is firing at wrong time. Here is the gif to show the problem.

I am typing the Chinese wording "你好" with a Chinese input keyboard in iOS.

1. The char "你" is inputted by the code "人火".
2. I type with the code "人火" and these two codes are highlighted in grey in the textbox. The input method is still not completed yet. The code "人火" should not be considered as a text change event. However, onChangeText is triggered.
   
3. After I select the char "你" in Chinese input keyboard, onChangeText is triggered twice.
   

React Native version:

System:
    OS: macOS 11.0.1
    CPU: (8) x64 Intel(R) Core(TM) i7-8557U CPU @ 1.70GHz
    Memory: 751.11 MB / 16.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 14.15.1 - /usr/local/bin/node
    Yarn: Not Found
    npm: 6.14.8 - /usr/local/bin/npm
    Watchman: 4.9.0 - /usr/local/bin/watchman
  Managers:
    CocoaPods: 1.10.0 - /usr/local/bin/pod
  SDKs:
    iOS SDK:
      Platforms: iOS 14.2, DriverKit 20.0, macOS 11.0, tvOS 14.2, watchOS 7.1
    Android SDK: Not Found
  IDEs:
    Android Studio: 4.1 AI-201.8743.12.41.6953283
    Xcode: 12.2/12B45b - /usr/bin/xcodebuild
  Languages:
    Java: Not Found
    Python: 2.7.16 - /usr/bin/python
  npmPackages:
    @react-native-community/cli: Not Found
    react: 16.13.1 => 16.13.1 
    react-native: https://github.com/expo/react-native/archive/sdk-40.0.1.tar.gz => 0.63.2 
    react-native-macos: Not Found
  npmGlobalPackages:
    *react-native*: Not Found

Steps To Reproduce

Provide a detailed list of steps that reproduce the issue.

1. Open https://snack.expo.io/@hkhermanho/textinput-with-chinese
2. Type any Chinese characters with Chinese input method

Expected Results

onChangeText should not be fire before the input method is done. It should be fired 2 times for 2 Chinese characters instead of 8 times.

Snack, code example, screenshot, or link to a repository:

https://snack.expo.io/@hkhermanho/textinput-with-chinese

まず、リンクされた Expo Snack の問題を、中国語入力メソッドを使用して iOS で再現します。説明されている入力シーケンス中に TextInput がコンポジションをどのように処理し、onChangeText がいつ発火するかを追跡します。コンポジションの完了後にのみ callbacks が発生し、中国語の 2 文字に対して 2 回発火すれば完了です。