How to reproduce:
1. Open the "SampleScene" Scene in the attached "movetest.zip" Project
2. Enter Play Mode
3. Hit space a couple of times which resizes the camera rect.
4. Game View does not change.
5. When you move objects around you can see that the area outside the rect just doesn't clear.

Expected Behavior: you should be able to change how the area outside is rendered.
Actual Behavior: The Game View seemingly doesn't change.

Reproducible with: 2017.4.32f1, 2018.4.7f1, 2019.2.2f1, 2019.3.0a12, 2020.1.0a1

Note: You can check the difference by pressing on the Main Camera and comparing The small window in the Scene View with a Game View itself.