Modal `formSheet` backdrop fade animation missing on first modal creating unsmooth experience.

Description

When presenting a <Modal> with presentationStyle="formSheet" and animationType="slide", the backdrop dimming overlay does not fade in on physical iOS devices. Instead, the dimming appears instantly without animation when the first modal opens, results in a jarring, unsmooth appearance when opening modals.

Native apps do not have this problem, so it is unfortunate that all react-native apps suffer from this visual downgrade.

The modal sheet itself slides up correctly, only the backdrop transition is broken.

Notably:

• The second modal's backdrop animates correctly
• Modal dismissal backdrop fade-out always works correctly
• The iOS Simulator works correctly - the bug only appears on physical hardware

This was originally reported against react-native-screens (https://github.com/software-mansion/react-native-screens/issues/2977), but the issue reproduces with React Native's built-in <Modal>.

Steps to reproduce

1. Create a fresh React Native 0.84 project
2. Use the reproduction code below
3. Build and run on a physical iOS device
4. Tap "Open Modal 1" — observe the backdrop appears instantly (no fade)
5. Tap "Open Modal 2" — observe the backdrop fades in correctly this time
6. Close both modals and repeat — the first modal's backdrop never animates

React Native Version

0.84.0

Affected Platforms

Runtime - iOS

Output of npx @react-native-community/cli info

System:
  OS: macOS 15.6
  CPU: (14) arm64 Apple M4 Pro
  Memory: 3.64 GB / 64.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 22.13.0
    path: /Users/kris/.nvm/versions/node/v22.13.0/bin/node
  Yarn:
    version: 1.22.22
    path: /Users/kris/.nvm/versions/node/v22.13.0/bin/yarn
  npm:
    version: 10.9.2
    path: /Users/kris/.nvm/versions/node/v22.13.0/bin/npm
  Watchman:
    version: 2024.12.02.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.16.2
    path: /Users/kris/.rbenv/shims/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.4
      - iOS 18.4
      - macOS 15.4
      - tvOS 18.4
      - visionOS 2.4
      - watchOS 11.4
  Android SDK: Not Found
IDEs:
  Android Studio: 2024.2 AI-242.23726.103.2422.12816248
  Xcode:
    version: 16.3/16E140
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.13
    path: /usr/bin/javac
  Ruby:
    version: 3.1.6
    path: /Users/kris/.rbenv/shims/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 20.1.0
    wanted: 20.1.0
  react:
    installed: 19.2.3
    wanted: 19.2.3
  react-native:
    installed: 0.84.1
    wanted: 0.84.1
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

Stacktrace or Logs

None

MANDATORY Reproducer

https://snack.expo.dev/@supermelle/modal-native

Screenshots and Videos

In this video it it shown, how the animation on the first backdrop is missing, and also how it is working on the second modal.

https://github.com/user-attachments/assets/ba417a57-1b14-44b2-a197-59d5f3ffb3fa

Commencez par le reproducteur Snack obligatoire et exécutez-le sur un appareil iOS physique, en comparant les premier et deuxième modals formSheet avec animationType="slide". Suivez le chemin de présentation intégré de React Native Modal pour la transition du backdrop. C’est terminé lorsque le backdrop du premier modal apparaît progressivement et de manière fluide sur du matériel physique, tandis que la fermeture et les modals suivants restent corrects.