I'm as dumb as they come, so take this with a grain of salt: I think he is describing (a theory about) physical reality. To give you a different perspective: You position his theory of the universe as a network of nodes along with distances/measurements. But if you think for a moment about the void that you have to cross to get from one object to another (like from our star system to another) what is it? If you put it under an electron microscope it doesn't reveal itself.

It's "nothing" as far as we're concerned but despite being intangible, despite being nothing, it has rules and laws that govern matter that traverses it just like every other part of our universe. So what is space itself? What is it composed of? You can't take a quick step outside of the universe to get a look under the hood because you are part of the universe. You can only talk about it in terms of it's rules and behavior–in the abstract.