When "Allow Fullscreen Switch" is NOT checked, if script API is used to change the Player from fullscreen to windowed mode, the Player remains fullscreen mode and switches to native resolution automatically.

Repro:
1. Download attached project and make sure the "Allow Fullscreen Switch" is unchecked in Player Settings
2. Build and launch standalone Player
3. If the Player does not launch into fullscreen mode, switch it to through the UI provided in the project
4. Try to switch it back to windowed mode via the UI in the project

Expected: The script API can dictate what mode the Player is in, despite the Player Settings in the Editor.
Actual: The Player does not switch from fullscreen to windowed mode with script API.

Reproducible with: 2017.4.32f1, 2018.4.7f1, 2019.2.3f1, 2019.3.0b1, 2020.1.0a1

Note: This bug does NOT happen when "Allow Fullscreen Switch" is checked.
The script API used for project is "Screen.SetResolution" https://docs.unity3d.com/ScriptReference/Screen.SetResolution.html