mixing URI query and URI Segment

[eluser]Jonathon Hill[/eluser]
So is this a bug?

Code:

// If the URL has a question mark then it's simplest to just
// build the URI string from the zero index of the $_GET array.
// This avoids having to deal with $_SERVER variables, which
// can be unreliable in some environments
if (is_array($_GET) AND count($_GET) == 1 AND trim(key($_GET), '/') != '')
{
    $this->uri_string = key($_GET);            
    return;
}

Since when does $_GET contain the URI string?? This doesn't appear to work at all - is it a bug? What am I missing?