This limitation must be built into security hardware used by iPhone so software couldn't do anything about it. I was under impression that it's how iOS security model works. If it's not and in fact this check implemented in iOS itself, it's much weaker protection and it's really looks like an intended backdoor from Apple.
It's not really built into ‘hardware’, it's enforced by the Secure Enclave, which is software-based and accepts software updates signed by Apple. It's secure against kernel exploits and third-parties, but not against Apple.
