Background
In my app I use CallKit, only to check if there is an ongoing call, and after adding that feature, my app got rejected because CallKit has been blocked in China:
Recently, the Chinese Ministry of Industry and Information Technology (MIIT) requested that CallKit functionality be deactivated in all apps available on the China App Store.
I looked for a way to fix this, apparently it's OK to check the phone's country code and just not use CallKit if it's in China.
My question
In all examples I found for doing this – e.g. Disabling Callkit from China Store Best Approach – the phone's country code was compared against both "CN" and "CHN".
Why compare to three letter codes in addition to two letter codes? I mean, the country code comes from iOS, it ought to be well defined what comes from that source.
I have tried comparing both two and three letter codes, but so far only come across two letter codes and I've only seen two letter codes in the docs – but I couldn't find a definite answer in the docs either.
