Is this a bug report?

Yes. Pull request will follow.

Have you read the Contributing Guidelines?

Yes

Environment

Environment:
OS: Windows 10
Node: 8.9.4
Yarn: Not Found
npm: 4.6.1
Watchman: Not Found
Xcode: N/A
Android Studio: Version 3.0.0.0 AI-171.4443003

Packages: (wanted => installed)
react: 16.2.0 => 16.2.0
react-native: https://github.com/expo/react-native/archive/sdk-25.0.0.tar.gz => 0.52.0

Steps to Reproduce

See snack: https://snack.expo.io/Sy_bHbM_z

1. Render SectionList, with initialScrollIndex prop specified
2. Watch how list items jump between first/second rendering

Expected Behavior

List items would render at a consistent position.

Actual Behavior

VirtualizedList with initialScrollIndex specified renders content in different positions for the first/second rendering, causing a noticable jump of the list items.

Reproducible Demo

https://snack.expo.io/Sy_bHbM_z