Invalid call to node_load in simplenews_mail_mail

In simplenews.module, function simplenews_mail_mail, line 1623, there's an invocation of node_load:

$node = node_load(array('nid' => $nid, 'vid' => $vid));

This always returns a null node for me (Drupal 6.8, PHP 5.2.4, MySQL Ver 14.12 Distrib 5.0.51a) on every invocation, meaning that no messages are ever mailed to the subscribers (although, interestingly, the test messages go ok).

Looking at the docs for node_load:

node_load($param = array(), $revision = NULL, $reset = NULL)

it allows either an array of arguments, or two scalar arguments: $nid, $vid (node and revision ids). I'm not sure how the array approach would work (perhaps it won't work unless there's only one revision for the node?), but by altering the call to node_load to

$node = node_load($nid, $vid);

everything burst into life... Was there a specific reason for using the param array??

Hope this helps someone.