I'm interested to see how this pans out - the reality is, the lions share of the costs for animated features have nothing to do with rendering. I'm concerned they are buying the worst of both worlds with this approach: they still have to create good looking art assets, they still need to animated them well, but they are further constrained by the confines of what they can do in a realtime engine, with a toolchain that is not optimized for this type of work.

I do think that there is a ton to be gained from tightly coupled previs pipelines that don't incur rendering overhead. Ideally the artists should be able to see what they are working on in a form that is as close to the final render as possible, but without the wait. Systems that can offer this with low overhead cut down on the amount of time the artists need to get the results they want tremendously, especially in situations where your team isn't big enough to have modeling, texturing, animation, fx and lighting departments that are completely siloed.