PS4 Pro utilizes a new type of rendering technology called checkerboard rendering that allows the developers to render at a higher resolution without sacrificing performance. This method is used in majority of the games that utilize the PS4 Pro extra power including some of the launch games like inFamous: Second Son and Knack.
Recently the Frostbite Labs developer Graham Wihlidal talked about the checkerboard rendering solution that they utilized for Battlefield 1 and Mass Effect: Andromeda on the PS4 Pro at GDC 2017. The reason developers have opted to render at 1800p CB resolution instead of native 4K or 1800p is simply because of the fact that the performance takes a hit with a higher rendering resolution. However thanks to some of the features like FP16 and rendering methods provided by the PS4 Pro, the developers have the ability to render at 1800p without sacrificing much of the image quality or performance.
As we can see, the difference in frame time, which effects the frame rate, is pretty huge between Battlefield 1 and Mass Effect: Andromeda on the PS4 Pro when rendered at native 1800p vs. using a checkerboard 1800p. This method saves performance while also giving the developers extra leverage to clear the image quality. We also learn that this checkerboard technique is different depending on how it is utilized by the developers in their game, and in the case of Frostbite engine, it appears to closely match native 1800p resolution.