What's really baffling to me about this claim is that Amos Burton or James Holden is each equivalent to like a 100 point GURPS character, starting Traveller character, or 1st to 3rd level D&D character. He's certainly not at the start of the story more than about 3rd level. In fact, in setting there might not be anyone who is equivalent to more than about 6th level in D&D terms. And this is probably verifiable by the author, because Expanse began life as a homebrew GURPS Transhuman Space game before it was a novel and so somewhere back there James Holden probably was a PC before he was a character in a novel. They are each about 25-30, have had a few hard life experiences, but are in no way at the start of the story high level characters in the setting. Rather, they are obvious RPG protagonists, because despite clearly being low level characters the high level NPCs are like - "Yes, we want to give you a job to save the human race." They are obviously Ta'veren, and the smarter NPCs can tell.