[my123]

It does not reduce the security level to at or below the one of any regular PC.

The bootrom bug requires DFU and physical access to be triggered, which is already game over on most systems. Apple also doesn’t solely rely on measured boot for the encryption keys (unlike default BitLocker configuration with TPM).

[tumult]

It was specifically a selling point of these computers. One of the headlining features. (As I said in my earlier comment, "with the claim that they had hardware security")