The author is advocating for a company that publishes proprietary software. And that it should not engage in Open Core because it does not work. I agree on this.
And then he suggests to create and maintain a Free Software on top of which the proprietary software is built. The proprietary software his company creates presumably contains dozens if not hundreds of such Free Software building blocks, ranging from OpenSSL to nginx and more. Creating a new one that is a direct dependency of the proprietary software may make sense.
I find this article interesting because it is the first time I heard this kind of confusion. There is no relationship whatsoever between Open Core and creating a generic building block on top of which a proprietary software is created. Both have coexisted for over a decade. Why would the author claim otherwise is something I do not understand.