"If you replace the battery in the newest iPhones, a message indicating you need to service your battery appears in Settings > Battery, next to Battery Health," said iFixit.
This happens regardless of whether third-party repair companies install a genuine battery, or a third-party alternative.
"Unless an Apple Genius or an Apple Authorized Service Provider authenticates a battery to the phone, that phone will never show its battery health and always report a vague, ominous problem," said iFixit.
iFixit confirmed that Apple is not throttling the performance of these users' iPhones, but maintains that the move is a "user-hostile choice" that will cause confusion.
"This ‘Service' indicator is the equivalent of a ‘Check Oil' light that only a Ford dealership can reset, even if you change the oil yourself," said iFixit.