Nier Automata is available now on the Xbox One. It is a great looking game that runs on the Unreal Engine 4 but it is evident after the Xbox One version that this was never developed with HDR in mind. While it is possible to play the game with HDR on the Xbox One X, the implementation here is rather wonky and can make the game look worse than the original version.
This was discovered by resetERA user EvilBoris who has shared his findings in a post with a detailed look at the HDR in the game. His analysis finds out that the HDR is simply a poor implementation that makes the color look like washed out instead of actually increasing their intensity as it is the case with a good HDR implementation.
The game is entirely in SDR and is expanded from 8bit to 10bit and then adjusted to fit into the appropriate place within an HDR ouput and then is sending the signal to the TV that the content is HDR.
Nothing is gained, in fact things that would have previously been darker now become lighter than then should be, resulting in a lower contrast image, washed out image.
This is the HDR equivalent of upscaling and claiming the game is a higher resolution than it actually is. But then actually up-scaling it incorrectly and reducing the resolution a bit.
I can’t really speak for Nier Automata but personally from my own experience with games that were later patched with HDR, like Witcher 3 and Crash Bandicoot N. Sane Trilogy, they don’t really look as good as games that were developed with HDR support in mind, and in some cases, can actually look worse.