The vc_mapping method in the custom WPBakeryShortCode block is reinvented on all pages?

Question

I’m creating my own custom block for WPBakery:

add_action('init', function() {
    class vcCatalogBlock extends WPBakeryShortCode
    {
        function __construct()
        {
            add_action('vc_before_init', [$this, 'vc_mapping']);
            add_shortcode('vc_catalog_block', [$this, 'vc_catalog_block']);
        }

        public function vc_mapping()
        {
            vc_map(
                array(
                    'name' => 'VC Catalog Block',
                    'base' => 'vc_catalog_block',
                    'description' => 'Company Catalog',
                    'category' => 'Blocks',
                    'icon' => '',
                    'params' => array(
                        array(
                            'type' => 'dropdown',
                            'heading' => "Select conference",
                            'param_name' => 'conference_id',
                            'value' => $this->get_conferences(),
                            'admin_label' => true,
                        ),
                    )
                )
            );
        }

        public function get_conferences()
        {
            $result = wp_remote_post(CRM_SITE_URL . '/api/conference/list');
        }

    }

    new vcCatalogBlock();
});

The vc_mapping method works on all pages! For what? This method should only work where the WPBakery visual editor is used (enabled).

Since in the vc_mapping method I access an external API, this request occurs on all admin pages!