Apple allegedly throttling older iPhones with degraded batteries
A user on Reddit by name TeckFire, has found that his iPhone 6S has been very slow after updating to iOS 11. But his brother's iPhone 6S Plus seemed to do just fine. After deciding to probe a bit deeper, he ran Geekbench 4 on his 6S and found that the scores were low. He ran the test again after replacing the battery and found that the scores were back to normal again.
TeckFire says that his battery could have worn out by about 20% at the time of running the first Geekbench test. He apparently got scores of 1466 Single and 2512 Multi. After replacing the battery, the scores went up to 2526 Single and 4456 Multi. This leads one to an inference that Apple could be slowing down phones that have degraded batteries in order to retain charge and prevent them from shutting down. The situation does not change even when plugged into AC power.
Apple is no stranger to throttling controversies, though. When Apple launched iOS 10.2.1 earlier this year, it claimed to have fixed a lot of unexpected shutdowns plaguing many iPhone 6 and 6S users. Users had reported back then that their phones slowed down considerably after the update but the unexpected shutdowns were apparently gone. A trip over to the Apple Community forums reveals that the update intentionally slowed down the CPU in order to avoid voltage spikes from select 'questionable' batteries, thereby preventing shutdowns. Not just CPU speeds, Apple was also accused by 'you-know-who' Qualcomm for reducing the LTE download speeds in the latter's X12 600 Mbps modem used in Verizon's iPhone 7 to match that of Intel's 450 Mbps modem in AT&T's iPhones. When the story broke out, Apple allegedly gagged Qualcomm to prevent customers from knowing the extent to which the LTE speeds were throttled.
If you're concerned about your iPhone slowing down, consider replacing the battery to give it another chance and check CPU scores before relegating it to (planned) obsolescence.