When using mw.util.getUrl with params, it seems that it creates an index.php url even if the wiki has short urls set up, which is what it did until it was changed in rMW687dc7cf57bdc74a80b2ae3176cda1facd535ee9.

var page = mw.config.get('wgPageName');
mw.util.getUrl(page);
mw.util.getUrl(page, {
    action: 'delete'
};