Reproduction steps:
1. Create a new project
2. Import URP and Google VR iOS packages via Package Manager
3. Create a URP Rendering Asset (read note 1) and set it as Graphics Pipeline Settings in Edit -> Project Settings -> Graphics
4. Go Edit -> Project Settings -> Player -> XR Settings (for iOS)
5. Enable Virtual Reality Support
6. Add a Cardboard Virtual Reality SDK
7. Set Stereo Rendering Mode to Single Pass
8. Enable FXAA and Post Processing on Camera
9. Build the project for iOS and deploy it using Xcode (use .xcworkspace for opening it in Xcode)

Google VR iOS 2.0.1 used for all testing:
Reproducible with: URP 7.3.1 (2019.3.5f1), URP 7.4.1 (2019.3.15f1, 2019.4.2f1)
Not reproducible with: URP 7.2.1 (2019.3.5f1)
Could not test with: 2018.4, 2020.1, 2020.2 and the latest URP versions because Google VR iOS package is not available (and gets removed if updating)

Reproducible with Metal
Not Reproducible with OpenGL ES 2,3

Notes:
1. To create a URP Rendering Asset right-click on empty space in the Project window, then go Rendering -> Universal Render Pipeline -> Pipeline Asset (Forward Renderer)
2. I am not sure if Google VR is directly related to the issue since the regression is in URP