Apple CEO Tim Cook said that a future update will allow customers to turn off the power management feature that has caused older iPhones to slow down or switch off. Notice that it will not be by default, Apple is just giving its users permission not to be throttled and they will have to find out how to switch it off themselves. Most Apple users will not switch it off because they don't know how the phone works. Apple's target market is technology for those who don't know anything about technology.
Cook said that the power saving feature was first introduced in iOS 10.2.1 and insists that Apple did explain what was going on, but he thinks that Apple should have been clearer.
The company did indeed mention that the shutdown issue was caused by uneven power delivery and explained that its power management system had been tweaked, but there was no clear notice that it could cause devices to operate more slowly at times.
Cook said Apple "deeply apologises" to customers who thought the company had other motivations. Like the rather good theory that Apple was secretly throttling the performance of phones to encourage users to upgrade to new phones.
Apple is introducing better battery monitoring features in a future iOS update, and Cook says Apple will also allow customers to turn off the power management feature, which is new information that the company has not previously shared.