Forum Discussion
Everyone except external users disappears form Group Visitors
See here too
https://github.com/MicrosoftDocs/OfficeDocs-SharePoint/pull/928
nenonix , Escalation team is saying that setting read permissions on "Everyone Except External Users" may (or will ??) revert to Edit caused by a background job on public group site and is a normal behavior..... Ticket closed!!!
It's a none sense to me. I asked them to document this behavior because it is not documented. They said they will... I'm eager to read user comments when they will document this !!
So why providing the option to change permissions on public group site if everyone will always have edit access anyway? Go find out....
Martin-Coupal I think you should join the discussion on GitHub or add feedback on the document in question. The docs are opensource now, so anyone can contribute. (I work on the freelance team that helps to resolve issues on GitHub and I saw this discussion while trying to figure out a change that mentioned this, but did not explain it very well). You can open a new issue on the content page that should be changed - perhaps this one: https://docs.microsoft.com/en-us/sharepoint/understanding-permission-levels (scroll to the bottom and add your feedback to "this page" to open an issue on GitHub) is where to request that this be documented.
nenonix , thanks for the link. I've just post a feedback on the page.