How to reproduce:
1. Open user's attached 'URP-postproc-bug.zip' project
2. Open 'SampleScene' Scene
3. Select UniversalRenderPipelineAsset_Renderer.asset in Assets folder
4. Set Render UI Event to After Rendering Post Processing in the Inspector
5. Notice that PostProcessing is applied in the Game View
6. Set Render UI Event to After Rendering in the Inspector

Expected result: Post-Processing is applied to the Scene when Render UI Event is set to After Rendering
Actual result: Post-Processing is not applied to the Scene when Render UI Event is set to After Rendering

Reproducible with: 2019.3.0b11 (7.1.1, 7.1.2), 2020.1.0a13 (7.1.1, 7.1.2)
Couldn't test: 2017.4.34f1, 2018.4.13f1 Package Manager is not introduced, 2019.2.12f1 Forward Renderer doesn't contain _AfterPostProcessTexture

Note: Render Final PostProcessing Pass renders _CameraColorTexture when Render UI Event is set to After Rendering, other Render UI Events render _AfterPostProcessTexture