Wiki Server Requires "All logged in users" set to R&W

I continue to try and resolve spurious issues and unpredictable behavior. Now, I'm trying to rebuild a group wiki page because I could not control any of the permissions on the existing page. The purpose of the wiki is only to provide a shared calendar among a small subset (call them managers) of the users in the workgroup.

In order to make it so that "managers" would be the only people who could read and write to this calendar, I tried to set the wiki permissions to support this:

managers read & write

all logged in users read only

all unathenticated users no access

I could not get this to work. The only way I can get it so one of the users in the manager group can create or edit events in the calendar is if I have "All logged in users" set to read and write, which to me defeats the purpose of groups.

Either something is still jacked up with my wiki permissions (I did migrate from SLS quite some time ago but have never felt everything was working really reliably) or I am misunderstanding how the wiki permmissions are supposed to work.

Can someone help me with this, please?