It's not saving the battery, it's saving the battery and aircraft, cause when the battery is empty for real it shuts off and the aircraft drops like a rock.
There is no reason you should ever still be in the air to even reach the forced landing...
Why not take a more responsible approach and land before the battery reaches a critically low level?
Flying until your drone drops out of the sky is far riskier than a controlled landing, which at least ensures it reaches the ground safely.