That's true for devices with a Secure Enclave, which the iPhone 5C does not have. As far as I know the key derivation is done entirely in software on older iPhones, but even if there was device-specific keying material it would be possible to dump that as well.
The CPU contains both the UID and GID on all iPhones (old and new). The Secure Enclave, if available, contains it's own UID for it's own key derivation.
