The set of subtabs on site-load compared to the question's subtabs is confusingly different. I've only just recently figured out how to navigate back to the site-load view (and the various subtabs it contains) by click on the logo for that stackexchange. It seems to me that the site-load view should load to a default tab (perhaps 'questions') or give some visual "selected" cue by adding a 'home' tab (or the like).
Actually, there is a visual indication of which tab is being shown: When none of the tabs is highlighted, you are watching the front page.
For the new users, the problem is understanding that the site logo is the link for the front page. A way to resolve it would be displaying the logo using as background color the same color used to highlight the tabs. it is true that normally the logo is placed to the left side of the tabs, but that is not true for all the sites; this means that the logo could not seem as a special tab, in those sites.
Probably a new tab would help the users, but I would rather not call it "Home"; "Front page" seems better, but I am not still convinced it is a good name.
I am used to sites where the logo is linked to the front page. It is true that in some of them there is also a tab for the front page, but that is something additional.
I would assume users are used to click on the site logo to return to the front page.