I wonder... Maybe the parallel with Willis being a henchman is intended, maybe this story arc is almost as much about Jason's dad as it is about Bizarro losing it or introducing this Solitary character.
Also, I must point out that when Jason said that about a promise being a promise until it isn't anymore, I also took it as Jason thinking about Bizarro breaking his promises to them, as much as him reflecting about his own promise to Bruce (linking it with Bizarro actually about to break that promise indirectly as well as with his introducing inner boxes a bunch of pages before).
Or maybe I'm seeing too much into it for a book that pretends to be mostly just fun with a few things to think about.