The "unexpected shutdown", as Apple called it, was a result of a voltage drop in the battery. Voltage drop occurs when the max current capacity of a battery is exceeded, it has nothing to do with battery age.
Also, when you experience a voltage drop you have generally exceeded the c-rate of the battery and caused some damage which increases it's internal resistance and further reduces the max current capacity of the battery.
The iPhones experiencing "unexpected shutdown" weren't very old, generally a battery is spec'd with a c-rate that takes into account degradation over time. The fact that Apple shipped software to limit the max current draw of the device demonstrates that this wasn't expected behavior AND they were attempting to hide it rather than own up to a defect that might result in a recall.
The "unexpected shutdown", as Apple called it, was a result of a voltage drop in the battery. Voltage drop occurs when the max current capacity of a battery is exceeded, it has nothing to do with battery age.
Also, when you experience a voltage drop you have generally exceeded the c-rate of the battery and caused some damage which increases it's internal resistance and further reduces the max current capacity of the battery.
The iPhones experiencing "unexpected shutdown" weren't very old, generally a battery is spec'd with a c-rate that takes into account degradation over time. The fact that Apple shipped software to limit the max current draw of the device demonstrates that this wasn't expected behavior AND they were attempting to hide it rather than own up to a defect that might result in a recall.