Hey guys, thanks for the perspective! (I'm the guy who wrote the article)
You're right, saying "16px minimum for all sites" was wrong. I have no idea where I heard the phrase "16px is minimum for accessibility", but I guess that just stuck in my head, and since I even found similar sayings in other sources, I took it to be true.
So umm, fake news I guess?
I revised the article to clarify that and left links that go into more detail on font size.
Thanks again. I appreciate everyone voicing their opinions.