Edit: Ah, no, because then the server would not know where to send the URL for the primarydomain folder.
Of course it would not know what to do unless you tell it what to do with additional .htaccess code. By Default a Server will load either an index.php, index.html or index.htm file. If you want the Server to load a different file then you have to tell it what you want it to load instead. You would do that with additional .htaccess code.