Is Apple slowing down old iPhones? It's a question that comes up again and again because iPhone batteries aren't easy to replace, and a new report from a popular benchmarking app suggests the answer is yes.

The founder of Primate Labs, which makes the Geekbench app used to benchmark performance of iPhones and other mobile and desktop devices, dug deeper into the numbers collected by the app -- after a popular Reddit post last week discussing the issue -- and published his findings Monday.

"It appears the problem is widespread, and will only get worse as phones (and their batteries) continue to age," John Poole wrote. " I believe (as do others) that Apple introduced a change to limit performance when battery condition decreases past a certain point."

Geekbench found slowdowns in the performance of iPhone 6s and iPhone 7 models after iOS updates. Poole theorizes that as the battery in an older iPhone declines, Apple slows down the phone's performance so the battery won't drain too quickly, and mentioned the iPhone 6 shutdown issue that Apple acknowledged late last year as a possible reason.