Could you please have a look on the following weird behavior of "Per app" strategy for the paid app?
If some Full/Status Bar mode is granted for the app (both system and user one), it works properly for the period while the screen is active. Once the phone goes to the Sleep mode (even in just 5 seconds after the screen is off), the same app will be run in normal mode (without selected immersion type), so I have to toggle the Immersion Manager status off/on (or re-select the mode from UI).
I'm running the stock Android 8.0 ROM on my Samsung S8 Active (not rooted), so required WRITE_SECURE_SETTINGS permission was granted through ADB console. Immersion Manager app is black-listed for the built-in Battery Optimizer and additionally locked within the phone task manager (to prevent any possible accidental closure).
Thanks in advance!