Mike, XFA is using the XF 'navigation_tabs' even listener so there are only three options available: home, middle, or end. It is currently omitting the value so it is using the default middle position. Now where it occurs within the middle is up to the system to decide.
If you want to disable it so you can manually add a link to where you want, enable debug mode on your site & then go into Development (tab won't appear unless you're debug mode) => Code Event Listeners => XF Arcade navigation_tabs and uncheck it so the listener is not active.