List flickering if `maintainVisibleContentPosition.startRenderingFromBottom` is set to true

Description

When maintainVisibleContentPosition.startRenderingFromBottom is set to true, only the bottom item is rendered at first. This is causing a flickering effect during list rendering.
It seems to be okay if maintainVisibleContentPosition.startRenderingFromBottom is set to false.

Current behavior

When maintainVisibleContentPosition.startRenderingFromBottom is set to true, only the bottom item is rendered at first.

Expected behavior

When maintainVisibleContentPosition.startRenderingFromBottom is set to true, items to fill the displayed area are rendered.

Reproduction

Expo Snack or minimal reproduction link:

The issue is reproduced in the fixture app
https://github.com/Shopify/flash-list/tree/921847d35cca043f438a441e9348bad358ffc0fd/fixture

(videos are slowed down so it's easier to see the issue)

https://github.com/user-attachments/assets/db5fdea6-ce47-4b0c-bea6-4b8bae075f84

https://github.com/user-attachments/assets/3e4a4b0d-de06-417f-9af0-0d996996dbe4

Platform

• iOS
• Android
• Web (if applicable)

Environment

System:
  OS: macOS 26.2
  CPU: (10) arm64 Apple M2 Pro
  Memory: 125.64 MB / 32.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 20.19.5
    path: ~/.nvm/versions/node/v20.19.5/bin/node
  Yarn:
    version: 1.22.19
    path: /opt/homebrew/bin/yarn
  npm:
    version: 10.8.2
    path: ~/.nvm/versions/node/v20.19.5/bin/npm
  Watchman: Not Found
Managers:
  CocoaPods: Not Found
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 25.2
      - iOS 26.2
      - macOS 26.2
      - tvOS 26.2
      - visionOS 26.2
      - watchOS 26.2
  Android SDK: Not Found
IDEs:
  Android Studio: 2025.2 AI-252.28238.7.2523.14688667
  Xcode:
    version: 26.2/17C52
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.9
    path: /usr/bin/javac
  Ruby: Not Found
npmPackages:
  "@react-native-community/cli":
    installed: 18.0.1
    wanted: 18.0.1
  react:
    installed: 19.0.0
    wanted: 19.0.0
  react-native:
    installed: 0.79.1
    wanted: 0.79.1
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: false

FlashList version:
2.2.0

Additional context

N/A

Checklist

• I've searched existing issues and couldn't find a duplicate
• I've provided a minimal reproduction (Expo Snack preferred)
• I'm using the latest version of @shopify/flash-list
• I've included all required information above

Start by running the linked fixture app reproduction with FlashList 2.2.0 and maintainVisibleContentPosition.startRenderingFromBottom enabled on iOS and Android. Compare the initial rendering with the expected behavior: items should fill the displayed area without flickering; use the provided videos as the visual reference.