I did find this message below the setting that requires a password for the Shed:
I don't know if this has changed since a previous version but it sounds like it might have. I don't see a way to over-ride this. It appears to be the (new?) built-in setting.
When enabled, users who have permission to access the forum will need to provide the password. Users who do not have permission to access the forum will not be prompted for the password. The password applies only to this forum, if this forum has subforums, the password will not be required for them.
Topics posted in a password protected forum will not show in any sidebar, header or footer blocks, and notifications for new topics and posts will not be sent.
I don't know if this has changed since a previous version but it sounds like it might have. I don't see a way to over-ride this. It appears to be the (new?) built-in setting.