Will definately not having the attachment name, that would be a large security issue if you have the filename script.php which has
PHP Code:
<?
while (1=1) {
require('http://url.com/attachment/script.php');
}?>
which would cause a loop to keep including itself and hence crash the server or other various things.
vBulletin 3 uses the attachment id as the filename, so that seems the most sensible thing to do.
Also the visible thing was actually a bug that was corrected so you should just leave it in.