I think it's worth re-iterating what whist said. This becomes an issue on Mobile, where only the stuff in the middle loads (shoutbox, latest posts, screenshots). It's unclear how to get to the forum index, especially since it's not shown.
The only way to get to the forum index is to click the "Home < Board index" link. Which funnily enough, still says "Home < Board index", but takes you to a different page (adds index.php to the url).
I think it would be more clear if the default page loaded just said "Home" and clicking the forums button took you to "Home < Board Index". And clicking home button basically does what it does now (loads the non-index.php URL).