The option is spec'd here https://docs.grabaperch.com/addons/events/page-functions/custom/, but is not implemented in the latest version of the app (as far as I can tell).

To resolve this, made the following changes to PerchEvents_Events.class.php.

Old Code (starting line 387)

        if (isset($opts['skip-template']) && $opts['skip-template']==true) {

            if ($single_mode) return $Event;

            $out = array();
            if (PerchUtil::count($events)) {
                foreach($events as $Event) {
                    $out[] = $Event->to_array();
                }
            }
            return $out; 
        }


        // template
        if (isset($opts['template'])) {
            $template = 'events/'.str_replace('events/', '', $opts['template']);
        }else{
            $template = 'events/event.html';
        }

        $Template = $this->api->get("Template");
        $Template->set($template, 'events');

        if (PerchUtil::count($events)) {
            $html = $Template->render_group($events, true);
        }else{
            $Template->use_noresults();
            $html = $Template->render(array());
        }

New Code

       // template
        if (isset($opts['template'])) {
            $template = 'events/'.str_replace('events/', '', $opts['template']);
        }else{
            $template = 'events/event.html';
        }

        $Template = $this->api->get("Template");
        $Template->set($template, 'events');

        if (PerchUtil::count($events)) {
            $html = $Template->render_group($events, true);
        }else{
            $Template->use_noresults();
            $html = $Template->render(array());
        }

        if (isset($opts['skip-template']) && $opts['skip-template']==true) {

            if ($single_mode) return $Event;

            $out = array();
            if (PerchUtil::count($events)) {
                foreach($events as $Event) {
                    $out[] = $Event->to_array();
                }
            }

            if (isset($opts['return-html'])&& $opts['return-html']==true) $out['html'] = $html;

            return $out; 
        }