Hrm. Maybe someone from SUAC could comment on what we’re missing (if anything) about the permissions, or if this is a bug.
In either case, I would say that training/policy is likely the best option here, since there will be some leaders who have Edit Advancement/Full Control permissions and serve as MBCs. If the intent is only to have a specific person (e.g. ASM assigned to serve a particular patrol) mark advancement Leader Approved, then making sure that everyone knows the policy, and ensuring that it’s regularly reinforced, will help set the practice in everyone’s mind.