Phew, finally found out what was wrong…
Query args should be as follows:
$cdm_front_query_args = array(
'post_type' => array( 'post', 'events' ),
'posts_per_page' => 9,
'meta_key' => 'pin_home_page',
'orderby' => array( 'meta_value_num' => 'DESC', 'date' => 'DESC' ),
);