The article feels very much like a thesis in search of support, which might explain the laser like focus on one particular data point that appeared to support the author's premise. It also explains why criticism of the original research is dismissed as "cancel culture" rather than taken as a sign to at least look for other supporting data.
The motivation makes more sense if you look at the rest of that substack (I wasn't familiar with it, so I poked around a bit). The author evidently has a deep interest in sex and gender role topics viewed through a particular lens. The second post I looked at was basically incel ideology 101, complete with Becky, Chad, and links to Jordan Peterson. I'll save you a click, but apparently teenage girls are depressed because they're not having sex with incel teenage boys.
Given the rest of that blog, it's probably not surprising the author managed to boil down a topic as complex as the development of societies into a simple explanation about sex, backed by a single data point that's out of favor with actual professionals in the field.