The company says some of that is due to the iOS 10.2.1 update that addressed unexpected shutdowns on iPhone 6, iPhone 6 Plus, iPhone 6s, iPhone 6s Plus, and iPhone SE. It would definitely be interesting if we were to find out that Apple isn't the only company doing this.
As mentioned above, the belief that Apple has knowingly slowed down iPhones on a regular basis to coax iPhone users into buying new iPhones has been around for years, but it actually became a reality this year, with Apple admitting it does slow down old iPhones starting in 2016.
Apple is already facing several class-action lawsuits in the US and Israel after admitting to slowing older iPhones as the batteries get older. "With the update, iOS dynamically manages the maximum performance of some system components when needed to prevent a shutdown", Apple writes.
That produced backlash headlines like this one: It's not just you: Apple really is intentionally slowing down older iPhones.
Apple also posted a new support article about iPhone Battery and Performance.
Apple's public apology is a good start and the reduction in price for a battery replacement should please many disappointed customers.
"Device use also affects the performance of a battery over its lifespan".
In its letter, Apple said it recognizes it needs to "regain the trust of anyone who may have doubted [its] intentions, and will be reducing the price of an out-of-warranty iPhone battery replacement from $79 to $29".
We now believe that another contributor to these user experiences is the continued chemical aging of the batteries in older iPhone 6 and iPhone 6s devices, many of which are still running on their original batteries. Apple's goal was to limit the processor speed to avoid these random shut downs and to put less strain on the batteries inside those phones.
In addition to the discounted battery offer, Apple said it also plans to roll out an iOS update early next year that will better allow iPhone owners to monitor the health of their battery and to understand if its affecting their phone's performance. In the letter, Apple acknowledges that customers might feel that Apple let them down.