I wouldnt be surprised if they had a backdoor into the Qualcomm chip that Apple decided to oddly still include in most of their US iPhones vs the international versions that come with their own internal modem
that Qualcomm chip that apple uses is a modem, so not sure it's that relevant to the phone's security in this case...
I wouldn't be surprised if they had a backdoor into the Secure Enclave. Apple is definitely a part of the US' NOBUS scheming, whether or not cops get to use it.
This extremely well hidden backdoor was an interesting find:
https://news.ycombinator.com/item?id=38783112