What is your exact question? To me it makes sense that you’d not want to use NoSQL if you’re dealing with data that’s already relational, and heavily leveraging features common in relational DBs that may not come out of the box with NoSQL DBs.

They’re saying basically that NoSQL DBs solve a lot of horizontal scaling problems but aren’t a good fit for their highly relational data, is my understanding. Not that they can’t get NoSQL functionality at eg the query level in relational DBs.