Hi Ceindeg,
First gotta say that interactions like these are one aspect of writing that I often enjoy. Now back to the topic at hand.

Your statement makes it seem like going below 16px is unacceptable. However that's not quite correct. 16px is a guideline, but now depending on whether the page is interaction heavy or not or if the font is a larger easily legible one like Monteserrat then it's still acceptable to go below this size. Now I'm answering this on my phone so I can't quite check the pages font but the aim of this guideline is to make sure everything is easy to read which in this case it mostly is! (Oh and yes i know the page isn't interaction heavy, just thought I'd mention it) Though I did notice a paragraph whose font was noticeably smaller than others and steps away from the uniformity that is important in UI (I'll be sure to go over this and other things in my future article on this topic)

These things are few among the many things that made switching from full-time UI design to UX, because I realized that data drives everything.

Though I'd like to remind you and anyone else reading that UI/UX has a lot of guidelines and rules of thumb, but rather than following them to the letter it's more important to understand why these guides are in place, and once you do, breaking the rules is possible as long as it doesn't take away from the purpose of the page.

Now obviously I only went into one aspect of this specific viewpoint on the page, and I'll rectify that by publishing an other article outlining negatives of the page too.

Thanks again for your comment, and have a wonderful day!