TECK, using your way, you need to add every single HTML file you have on your site as a new template, and then have a different PHP file to call each of this template.
My way, the html.php file automatically takes any HTML file on your file server and inserts it into the site. There is no need to add the HTML file into a vB template.
Using my hack, adding HTML files into your forums is as easy as changing the URL filename.
Your PHP code doesn't work for automatically including HTML files into vB. Trust me. There is not even a $file variable to get the HTML filename.