it appears to be.
as a test i created a template with multiple require once lines to the same file:
<?php
require_once("../phpinfo.php");
require_once("../phpinfo.php");
require_once("../phpinfo.php");
?>
<?php
require_once("../phpinfo.php");
require_once("../phpinfo.php");
?>
<?php
require_once("../phpinfo.php");
?>
<?php
require_once("../phpinfo.php");
?>
<?php
require_once("../phpinfo.php");
?>
when i applied this to a page, the results was:
<?php
require_once("phpinfo.php");
require_once("../phpinfo.php");
require_once("../phpinfo.php");
?>
<?php
require_once("phpinfo.php");
require_once("../phpinfo.php");
?>
<?php
require_once("phpinfo.php");
?>
<?php
require_once("phpinfo.php");
?>
<?php
require_once("phpinfo.php");
?>
It seams Dreamweaver will only alter the path of the first require_once() statement in an individual php code block.