I think this app wakelock the screen so it always on, but then replace display with all black image so it looks like screen off.
How to know? Use a charger.
When screen really off, notification LED should turn red (indicate of charging when screen off)
But when use this app, LED blinks only once then come off, and the display black condition is slightly different than before.
Another proof, use Quickmemo button
You can screen capture the screen off!
In original screen off you can't capture screen (because it really doesn't display anything)
No wonder it drains the battery.
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