Reproduction steps:
1. Open attached project "Project.zip"
2. Change the platform to iOS and Build
3. Open the info.plist in the Xcode generated project. You will see that the "Launch screen interface file base name" field is set with "OriginalsSplash.storyboard"
4. Build and Run the Xcode project on a device

Expected result: There should be no grey screen between the storyboard launch screen and the first Unity scene.
Actual result: You will see a gray screen between the storyboard launch screen and the first Unity scene.

Reproduces on: 2018.4.18f1, 2018.4.19f1
Does not reproduce: 2018.4.17f1

Devices reproduced on:
iPhone 11 iOS 13.3.1
iPhone 6S iOS 13.3.1

Note: Changing the "Launch screen interface file base name" field in the .plist with "OriginalsSplash" fixes the issue