Apple doesn't manufacture the batteries. And you can't magically make batteries that perform identically. Every battery made has variation in it and that variat

Apple doesn't manufacture the batteries. And you can't magically make batteries that perform identically. Every battery made has variation in it and that variation can't be seen until it starts causing failures. The change would have been to simply advertise the service life was shorter than it actually was, to account for various worse batteries, but the long tail of worse off batteries would have still been there regardless.