Comment by 1st1

The point of that blog post is to look at both performance and usability.

MongoDB has a way to fetch data the way we needed and the way other databases fetch it in our benchmarks. We tried just that: the performance is roughly the same anyways. It's up to MongoDB users how exactly they store the data and how exactly they query it, but it's nice to know that their query language is capable enough.

I think that it's pretty obvious that not a lot of users query data like that in MongoDB and instead just store denormalized data. That's not the point of that blog post though.