I'm using the XML-forms module separate outside the context of the whole Islandora package or FC. So I'm not sure how this influences (if at all) Islandora itself.
Our use case is that we are directly using the output of Islandora XML forms. Using saveXML(). We are also sometimes viewing this output in a text editor, we would like to enable pretty formatting .
$xml_form = new XMLForm($form_state);
$document = $xml_form->submit($form, $form_state);
A PR has been submitted here: