Back in late 2017, a Reddit user benchmarked his iPhone before and after replacing its battery and found that its CPU performance improved following the battery change. Apple later admitted that it intentionally throttled phones with aging batteries and apologized by offering out-of-warranty battery replacements for $29, $50 less than usual. The tech giant also added a lengthy explanation in its support pages and rolled out a Battery Health screen, which can tell you if it's time to get your battery replaced.
The CMA investigated the issue when it blew up and raised concerns that people might have tried to repair or replace their phones if they weren't aware that updates could slow down their devices. Although Cupertino hasn't been keeping users in the dark for over a year when it comes to this particular matter, CMA says Apple's pledge "locks the firm into formal commitments always to notify people when issuing a planned software update if it is expected to materially change the impact of performance management on their phones."