^And Mr. Bennett (and any other ST novel author) would probably be the first to tell you that the novels aren't canon. That's not to say they aren't good or that you shouldn't feel that they enrich your personal feelings of what you believe. But as far as the show is concerned, they are not authoritative.
Now to answer your question: The Sphere Builders were from the 26th century of an alternate future where the Expanse had grown from the 22nd century to envelop the entire quadrant (or something like that). But in reality, they were nothing more than a plot device. That's why there was little to no character development for them in the show.