They're creating amalgamations, or at least one, for show. It goes back to the should/shouldn't morality of the first film. And to be fair, this is Jurassic World, it's a new park controlled by new characters making money from their ability to genetically create and control dinosaurs. This isn't the first book, nor is it the first film. I think the dinosaurs will mostly look just like what we've seen before, with the exception of this one animal that has been wildly spliced. As far as the tamed dinosaurs, it seems like people read that and their minds picture characters riding them, but I don't get that from it. They simply sound like they're genetically created to be domesticated and that they're further tamed and conditioned by trainers.
It sounds like this park is out of control and run by a bunch of yes men that want to keep making money so they start to experiment with what they can actually do with the dinosaurs. They're afraid that if they just keep the same animals around that visitation will begin to stale and diminish, and the park sounds really, really expensive so they feel the need to introduce new things to the audience. It makes sense. What I can say is that if this were just Jurassic Park 4 and the plot is yet another contrived reason for some of the same returning characters to go back to the island, which they never would unless forced, I would be less interested. Jurassic Park 3 did that and while it was brief fun, it was forgettable and added zilch to the story.