@Displacement activity
The processor IS customized. Every CPU from the A6 (used in the 5 and 5c) and on is a fully custom design done by Apple, so any references to the capabilities ARM CPUs have is not really relevant. Apple created their own design that implements the ARMv8 instruction set, which bears no resemble to ARM designed cores like the A57, A72, etc.
In the iPhone 5S and newer they also designed a second ARM CPU on the same SoC which is the "secure enclave" that runs an L4 microkernel completely separate from and independent of the iOS kernel that only communicates with iOS used a tightly defined and highly limited communications channel so any bugs/exploits in iOS can't be used to exploit the secure enclave.