According to The Verge, Apple said that it is not slowing down older iPhones to urge people to upgrade to newer models.
However, the company admitted to addressing an issue with devices containing older lithium-ion batteries that result in unexpected shutdowns.
"Our goal is to deliver the best experience for customers, which includes overall performance and prolonging the life of their devices. Lithium-ion batteries become less capable of supplying peak current demands when in cold conditions, have a low battery charge or as they age over time, which can result in the device unexpectedly shutting down to protect its electronic components," the company said in a statement.
"Last year we released a feature for iPhone 6, iPhone 6s and iPhone SE to smooth out the instantaneous peaks only when needed to prevent the device from unexpectedly shutting down during these conditions. We've now extended that feature to iPhone 7 with iOS 11.2, and plan to add support for other products in the future," it added further.
Earlier, Geekbench developer John Poole had mapped out performance for iPhone 6S and iPhone 7 over time and concluded that Apple's iOS 10.2.1 and 11.2.0 updates introduce a throttling effect for various devices.
Geekbench also reported that iOS 11.2.0 introduces similar issues for iPhone 7.
Apple's fix appears to be throttling the CPU to prevent the phone from randomly shutting down.
However, some Reddit users had reported that replacing their batteries has returned performance and CPU clock speeds back to normal.