Some of the most profitable ventures this century have been objectively illegal, but when you know you won't go to prison for violating the law, why would you care to follow it?
It seems utterly absurd to me that anybody should be able to issue a copyright claim on a collection of colors and fonts. Copyrights are issued to logos and slogans, not design systems.
The author (and myself, coincidentally) used to work at WP Engine. I still have friends there, I could still describe their infrastructure if I had to. How am I not to interpret myself as "affiliated?"