Try to find hard facts about this on the Internet and don't forget to report back if you found any.
There are some measurements of very old iPhones to be found (no info how theses were obtained) but in general we simply don't know how good or bad the measurement results really are. My understanding has always been that the sheer number of different mics used in Apple devices is limited compared to Android phones and that Apple provides some sort of generic calibration info for the class of mic in use (not the individual item, of course).
The question mainly is: If we disregard absolute SPL (which we can for RC), are those built-in microphones still linear enough (over frequency and sound pressure!) to handle the range between roughly 40 Hz and 400 Hz?
The ridiculous humps we have seen from many internal mics in the 8 to 10 kHz region clearly show how limited there quality really is. And this is nothing, even a calibration file can resolve. In the end, for really useful RC we need a good quality microphone in the first place and the ability to handle calibration files, indeed.