If I use "Graph Explorer" (https://developer.microsoft.com/en-us/graph/graph-explorer) with a normal user, I can't read all groups ("Insufficient privileges to complete the operation."). That's the behavior I want.
But if I use "Azure AD Graph Explorer" (https://graphexplorer.azurewebsites.net) with the same user, I can read all groups.
Why ?
UPDATE
With my normal user, I can also create a group: User in AD
Group creation: Azure AD Graph Explorer group creation

modify permissionsin the left of it. - Joy Wang-MSFT