iPhones have anti-hammering already. The Secure Enclave counts password attempts and enforced a lockout period (and wipes the keys after 10 attempts if configured to do so).

There was an attack years ago, where you could kill power to the device after failing the attempt but before it incremented the attempt counter, but they fixed that, and that may have predated the Secure Enclave anyway (and required taking apart the phone, which I assume this on-premises device doesn’t do).