UWP Games on Xbox One to get access to more hardware resources on Xbox One this Fall
There are a couple of ways games can be developed for Xbox One. One is using Xbox development kit which gives games full access to Xbox Resources, then you have games which are developed using UWP, ID @ Xbox and Xbox Live Creators Program. All these later ones are limited when it comes to access hardware resources on Xbox One.
This all happened because of the convergence between Xbox One and Windows Platform. Xbox One essentially runs on Windows 10 under the hood, except that it is heavily customized. Windows Store is now on the Xbox, and there are many apps that are available on Xbox One, Windows 10 and on Windows 10 Mobile as well.
The major difference between games developed using UWP and the one with Xbox One Kit is that UWP games have access to shared Windows Environment to communicate with other UWP apps just like they do on Windows.

Coming back to the topic, Microsoft has announced that it will let UWP get more access to resources on Xbox One when the major rollout of Fall Creators Update is rolled out. As of now UWP games can access 4 shared CPU, and 1 GB RAM, and can use only 50% of GPU for Direct3D11-based games. This will increase to 6 CPU cores, 5GB of RAM, and complete access to the GPU for Direct3D12-based games.
So why is Microsoft opening up? There are many reasons, and the primary is to push UWP, and secondly, games like Fallout and others can perform well, and the blame doesn’t go on Xbox One. I am pretty sure using Xbox Game Development Kit is definitely complex than using UWP and for small game publishers with more resource in hand can do well.