I really don't understand why his editors don't just provide him a team, like a tv show writing room, and he can bounce ideas off them and have them mechanically churn out his ideas. He could knock it out in a few months and be a hero and put it all behind him cleanly then.
Same with his parallel construction of lore using repetition of similar but distinct stories.
Simply saying "this is the truth" or "this is what happened" would not be the same, and I dont think many fanfic authors could pull it off convincingly.
I find the idea kind of revolting, but I am also surprised that collaborative writing is so rare. I suppose it cuts to the question of what the point of writing the book is in the first place.
It is hard to think of a recent example aside from the expanse by "James S.A. Corey"
I suspect it's less rare than we think it is, especially if you consider how much editing a lot of editors end up doing.