There is a bug in FlatList which reverses scroll direction for inverted FlatLists when the fling gesture is used in Android Pie devices. The fix is to change some code in ReactAndroid (in react-native module). However, in order for the changes to take effect, we need to build react-native from source.
The PR for this issue has been accepted by the react-native team; however, this feature wasn’t able to make it into the latest release (0.57.5). I suspect even after it comes out, I will not be able to use it until potentially a new update of your react-native fork comes out. So, I was going to try and fix this issue myself in the meanwhile. Hope this is a compelling reason to ask this question.