Hi,
Yes, if you set created in the status override setting of the plugin, you don't need to change the line $confirmed = array($config->get('invoice_order_statuses', 'confirmed')); of the plugin as the override will be used.
And the other change looks good. So I don't see why it wouldn't work.
It should at least generate an error or something. That would require some debugging to see which condition prevents the plugin from adding the PDF.
In the plugin file, you have 4 conditions which can stop that process:
// Valid order type
if(!empty($data->data->order_type) && $data->data->order_type != 'sale')
return;
// Valid email
if(empty($data->mail_name) || !in_array($data->mail_name, array('order_status_notification', 'order_creation_notification')))
return;
// Valid status
if(empty($data->data->order_status) || !in_array($data->data->order_status, $confirmed))
return;
//
$invoice_id_required = $this->params->get('invoice_id_required', 0);
if(empty($data->data->order_invoice_id) && !empty($invoice_id_required))
return;
try removing the conditions one by one to see which one is blocking the process from adding the PDF.
Once you find the condition, that will help understand why it doesn't work.