Problem with notification mod

I used some instructions to auto-subscribe user groups found here:
https://editflow.org/extend/auto-subscribe-user-groups-for-notifications/

And added the code to my functions with my actual array of user groups I want notified when a post’s $new_status is set to “publish”……but it isn’t working. None of the users in the two user groups in my array are getting the notification when a post is scheduled (future date). I checked the WP Codex, and there is no ‘scheduled’ status, a post is considered to be changed to ‘publish’ when it is scheduled.

Here is my actual code added to my functions.php:

// Auto-subscribe user groups to notifications when post is scheduled or published
function efx_auto_subscribe_usergroup( $new_status, $old_status, $post ) {
    global $edit_flow;
    if ( 'publish' == $new_status ) {
        // You'll need to get term IDs for your user groups and place them as
        // comma-separated values
        $usergroup_ids_to_follow = array(
             587,679
            );
        $edit_flow->notifications->follow_post_usergroups( $post->ID, $usergroup_ids_to_follow, true );
    } // Return true to send the email notification, false to not send
    return $new_status;
}
add_filter( 'ef_notification_status_change', 'efx_auto_subscribe_usergroup', 10, 3 );

What might I be doing wrong? Any help would be gratefully appreciated!