If you want to disable Jetpack related posts for specific custom post types then this code snippet could be helpful to you to achieve just that.
Please Note: This snippet has been stopped working all of sudden and I would try to replace it with the working one as soon as I find the solution.
/* Advanced Scripts Method to Add This Snippet */
function sw_jetpack_disable_related_posts( $options ) {
if ( is_singular( 'custom-post-type-name' ) ) {
$options['enabled'] = false;
}
return $options;
}
add_filter( 'jetpack_relatedposts_filter_options', 'sw_jetpack_disable_related_posts' );