Hi,
In reality, the screen toggle OFF then ON. But if you have a lock screen with pattern or multiple user account, it opens lock screen or multi user screen.
I think just a few people use this feature because it reduce the FOV. But I could see to add a checkbox or toggle button to make it auto apply on device/QGO start.
Anyway, if you love QGO, don't forget this page ;-)
https://anagan79.itch.io/quest-games-optimizer/devlog/755873/ratings-reviews