Apple don't do this specially.. It's jus when a battery gets older, it doesn't hold a charge as well and can unexpectedly shut down if it's put under too much stress. Apple's software prevents that from happening by slowing performance.
Just read a little bit about lithium batteries and about their performance.
News and Happenings
APPLE ADMITS SLOWING DEVICES
Submitted by Bubble, 22-12-2017, 12:57 AM, Thread ID: 66165
Thread Closed
RE: APPLE ADMITS SLOWING DEVICES 08-04-2018, 07:28 PM #33
08-04-2018, 07:28 PM
#33