The problem with getting hung up over some written policy is that a gov policy will always try to be vague and leave all options open. But in real life any civil servant around for some time will know what is the "real" policy as opposed to the written one.

For e.g., there is no written policy to say that only an AO scholar can be a perm sec, but everyone with half a brain knows if all you have is a first class honors from NTU/NUS, you will never make it past Senior Director/ CE of a small board even if you are the best ever performing staff they ever had. In SAF, unwritten policy means no scholar no star.