Works on my 1.17

Likewise.

"Admin" is the normal wiki sysops we're familiar with which do deleting/protecting/blocking/etc.

In order to manage user rights, you must be a bureaucrat (and have 'userrights' permissions), or be specially configured to add/remove specific rights (eg: $wgAddGroups, etc). Probably the "Tester" user doesn't have user-changing rights on prototype, meaning you *shouldn't* see the user rights management link.

You can confirm this by going to [[Special:UserRights]] on Prototype directly. You should still get an access denied message.