Why does the tv/renders/getinputs processor use modManagerController ?

/**
 * Simulate the TV manager controller to get TV input renders
 *
 * @package modx
 */
class TvInputManagerController extends modManagerController {
    public $loadFooter = false;
    public $loadHeader = false;
    public function checkPermissions() {
        return $this->modx->hasPermission('view_tv');
    }
    public function loadCustomCssJs() {}
    public function process(array $scriptProperties = array()) {}
    public function getPageTitle() {return '';}
    public function getTemplateFile() {
        return 'empty.tpl';
    }
    public function getLanguageTopics() {return array();}
}
class modElementTvRendersGetInputsProcessor extends modProcessor {
    ...
    public function process() {
        $context = $this->getProperty('context',$this->modx->context->get('key'));

        /* simulate controller with the faux class above */
        $c = new TvInputManagerController($this->modx);
        $this->modx->controller = call_user_func_array(array($c,'getInstance'),array($this->modx,'TvInputManagerController'));
        $this->modx->controller->render();

        $renderDirectories = array(
            dirname(__FILE__).'/'.$context.'/input/',
        );

        /* allow for custom directories */
        $pluginResult = $this->modx->invokeEvent('OnTVInputRenderList',array(
            'context' => $context,
        ));
        if (!is_array($pluginResult) && !empty($pluginResult)) { $pluginResult = array($pluginResult); }
        if (!empty($pluginResult)) {
            $renderDirectories = array_merge($renderDirectories,$pluginResult);
        }

        /* search directories */
        $types = array();
        foreach ($renderDirectories as $renderDirectory) {
            if (empty($renderDirectory) || !is_dir($renderDirectory)) continue;
            try {
                $dirIterator = new DirectoryIterator($renderDirectory);
                foreach ($dirIterator as $file) {
                    if (!$file->isReadable() || !$file->isFile()) continue;
                    $type = str_replace(array('.php','.class','.class.php'),'',$file->getFilename());
                    $types[$type] = array(
                        'name' => $this->modx->lexicon($type),
                        'value' => $type,
                    );
                }
            } catch (UnexpectedValueException $e) {}
        }

        /* sort types */
        asort($types);
        $otypes = array();
        foreach ($types as $type) {
            $otypes[] = $type;
        }

        return $this->outputArray($otypes);
    }
}

 public function render() {
        ...

        $this->modx->invokeEvent('OnBeforeManagerPageInit',array(
            'action' => $this->config,
        ));

        ...

        $this->modx->invokeEvent('OnManagerPageBeforeRender',array('controller' => &$this));
        ...
        $this->firePreRenderEvents();

        ...
        }

        $this->firePostRenderEvents();
        $this->modx->invokeEvent('OnManagerPageAfterRender',array('controller' => &$this));

        return $this->content;
    }