That code appears to be correct.
However, we cache results for related posts for 12 hours so your site does not have to contact WordPress.com on every page load; it could very well be why these tags haven’t been excluded yet.
If the posts still appear 12 hours after you’ve made those changes, could you post a link to one of the posts where you experience the issue, so I can take a closer look?
If you want your site URL to remain private, you can also contact us via this contact form:
http://jetpack.me/contact-support/
Thanks!