Unfiltered posts with "featured" appearing on /blog

Before the new /blog design, posts in the unfiltered category did not appear on /blog. I think if the post contained featured: yes in the frontmatter, it resulted in a blank block on the index page (not ideal, which is why we do have documentation to remove it: https://about.gitlab.com/handbook/marketing/blog/unfiltered/#review)

I noticed before a new featured post was published today that an Unfiltered post (where featured: yes had been left in the frontmatter) was appearing as the featured post on /blog.

Is there a way to prevent this? As mentioned above we do ask people not to include this in the frontmatter but it does happen occasionally.