Honestly there are worse things to write about. I too am a hard nerd who migrated from backend to frontend and dabbled in design. The discovery of typography, design rules, graphing principles, etc. felt to me like a revelation far outstripping the initial project(s) that inspired them. I read _The Elements of Typographic Style_ (Bringhurst) and Tufte and I read Nielsen's blog every day (back when it was at useit.com).
I wish in retrospect I'd written an article like this one; the wonder is genuine, and the satisfaction from the discovery of heretofore-invisible but trivially demonstrable rules is significant.
Finally, would point out that the author of this piece currently does not have any cards for sale, because they are sold out. :) So not only would it be ethically _ok_ to write an interesting piece that as a side-effect did some art self-promotion (if that were for example the reason the cards sold out,) but we know that, now and going forward, this article _cannot serve as a sales funnel_ because there is nothing being sold!
So, no, this article is fine and the cards are very interesting. I wish I'd been able to order a set, frankly