The ideas and conclusions remind me of OpenBSD’s pledge too. They privilege separate a lot of their in house software so the a bit that talks to the internet is separated as much as possible from the bit that does parsing, for example. But that was a just best practice they tried to follow with no way of enforcing it. Once pledge was created they found violations as programs started being killed for using disallowed syscalls. For their use capability based security enhanced and proved something they did already just informally.