It should work like that - does for me; are you sure there's not some other problem to do with using the Flash plugin in your mozilla - might be a problem there - does the demo in that article work okay in your same browser?
But NB - the technique described in that article doesn't work in Win IE5.0. To make it work, compliant, *and* get IE5.0 support, I eventually had to do this:
<!--[if IE 5]>
<![if ! IE 5]>
<param name="movie" value="home.swf" />
Which is ridiculous I know, and it gets worse - inverse conditional comments (by which I mean, NOT conditions) don't work properly in IE5.0 either - they do actually work, but the closing <![endif]> shows up as literal text on the page, so you have to surround the object in a DIV or something and set its text colour the same as your background!