Folders inside a shared notebook are one of two things, and they are not simply "shown" and "hidden".

Open is visible to every member. Naming people on an open folder does not hide it from anyone — it caps them, dropping those people to read-only while everyone else keeps their usual access.

Restricted is an allow-list. Only the people named can see it at all, plus the notebook's owner and managers, who always can.

So use open with caps when everyone should read something but only some should change it, and restricted when some people should not know it is there.