Thank you! This is the most important technical point about this whole thing. All the talking about the SE (fascinating as it may be) is irrelevant. All strong crypto that is based on a private key being kept in a secure vault at some corporation does have a backdoor. The keeper of the key can be compelled to use it to sign something.
This is exactly why this would be such a dangerous precedent. Government giving software specifications that are signed with a vendors public key. In this case, it's a one off but it's a step into the direction of "upload a screen-shot of the phone's display every minute to ftp.nsa.gov with your next iOS update". And no SecureEnclave will protect against that. It will just be a OS update signed by Apple.