This way no cookies will be placed which helps with both GDPR and Third Party Cookies. Unfortunually the oEmbed field does not recognize this url, while this is actually what is the url when you get a Privacy friendly embed script from Youtube itself.
The oEmbed field of Meta Box uses the WordPress function wp_oembed_get() to check and save the URL that is in the list of provider URLs and the nocookie Youtube URL isn't in the list. Check the file wp-includes/class-wp-oembed.php line 53.
When the WordPress core issue is fixed, you can use the nocookie Youtube URL on your site.