For example, they could have altered the calibration of the battery indicator so 0% charge corresponds to the charge level where random restarts/throttling starts to occur.
Calibrating for a new "0%" effectively lead to a "shorter battery life".
I don't know the intricacies of these options, but I can make a guess. The point which a phone resets isn't accurately predicted. Some user actions may cause larger voltage drops than others. For which action do you calibrate to 0%? What if you only do that action once a day? Is this trade off worth sacrificing 1% of your full capacity? What about 10% or 30%?
That seems almost useless. Certainly worse than having a slower phone that has hours of battery life.