Hi Kara,
You should use the choice value in lower case.
[
'name' => __( 'Save As', 'your-text-domain' ),
'id' => $prefix . 'save_as',
'type' => 'radio',
'options' => [
'draft' => __( 'Draft', 'your-text-domain' ),
'publish' => __( 'Publish', 'your-text-domain' ),
],
'std' => 'draft',
'required' => true,
'inline' => false,
],
And the code to update the post status is
add_action( 'rwmb_save_as_after_save_field', function( $null = true, $field, $new, $old, $object_id ) {
$my_post = array(
'ID' => $object_id,
'post_status' => $new,
);
wp_update_post( $my_post );
}, 10, 5 );