Yes, your suspicions have been confirmed. Apple is intentionally slowing down your iPhone as it gets older. Yesterday, Apple admitted it had been secretly throttling the performance of older iPhones. The throttling affects iPhone 6, 6S, and 7 users at the moment, but it may likely affect future iPhones until further notice. Below is the official statement from Apple:
“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.
“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.”
The throttling accusations first surfaced on Reddit, social news aggregation, web content rating, and discussion website. A Reddit member shared Geekbench results taken before and after the battery in his iPhone 6s was replaced. He claimed that performance on his iPhone 6s sped up drastically after replacing a battery with a wear level “around 20%.” Below is the result of the test with GeekBench.
You can read the results of other tests conducted by Primate Labs founder John Poole which showed some aggregate Geekbench data that shows a correlation between lower processor performance and degraded battery health.