The level of understanding that most people have about online tracking is just really, really low, and this author probably wouldn't know about any of this if Facebook didn't have that particular page.
Edit: yes most likely the author is someone that may be seldonmly writing for the site, or just sells his texts and doesn't really pay attention/care where this is posted.
So with regards to BuzzFeed I'm very aware of what garbage their site is. Right now on BuzzFeedNews I see 9 third party domains running ads or tracking pixels via JavaScript.
Ironically, one of those 9 is Facebook. So Facebook is tracking the people reading this article about how Facebook is tracking them.
But most people aren't technologically savvy enough or can't be bothered to run tools like these, and just browse the internet with basically no understanding of what is happening as they do.
I find it hard to believe they looked into the subject and didn't run across these. But I suppose it's possible.