I look forward to seeing if Apple makes any changes in the fork they ship with the OS: https://github.com/apple-oss-distributions/OpenSSH.

"Updated sandbox for privilege-separated pre-authorization sshd process" is listed as a modification to the open-source project, but I suspect this is out-of-date.

Deprecated since Mountain Lion. https://issuetracker.google.com/40474030

It’s what Apple experimented with before they came up with the current entitlements system.