It's not at all a dumb question :)
As Matt alluded to, the low poly art style is just meant to be used for prealpha testing. Alpha/Beta testing as well as the full game will be at the previously seen hi quality graphics.
Doing Prealpha testing in the low poly art style simply allows them to have a much quicker asset implementation so they can add things into the testing phases at a quick pace. Later all they will need to do is swap the low poly assets for the full fidelity assets, and since it's already in the UE4 engine it will basically be converted from prealpha to alpha. :D