The app doesn't Pause even though 'run in background' is unchecked

In older projects, the VR app stops working when take off the HMD (uncheck 'run in background')

window build
Unity Version : 2019.2.5f1
Oculus Integration version : Unknown (+Oculus Desktop)
Oculus Rift S

The latest version of the project is not affected by 'run in background'.
it always run in background (despite taking off the HMD)

window build
Unity Version : 2020.3.18f1
Oculus Integration version : 33.0
Oculus Rift S

Perhaps I should implement the Pause function myself? I don't know why this happens. please tell me how