So far this has been tested on Mac deploying SunTemple to an iPhone 7 (10.3.3).
It occurred with both Launch On and File Package.
This does not occur when deploying StrategyGame from the same Mac to the same iPhone.
1. Download SunTemple from the Launcher
2. Load it in the editor
3. Connect an iOS device and choose Launch On
RESULT: The app icon added to the device's home screen is generic instead of the custom icon for the app
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-53493 in the post.