It has a DSP to do it, though. If the XBOne had to do this on the CPU or GPU in realtime (if it were even possible) it would make disk playback a lot less power-efficient.
There's no strictly-defined speaker layout for those formats, either. I only have the two additional ceiling mounted speakers for Atmos/DTS-X and my receiver asks me to select where, of the 3 (IIRC) possible positions, I mounted them so when it wants to put a sound on my upper right at 10 degrees it knows how much of the sound to put on the Right-Front and how much to put on the Top-Center-Right and how to delay the sound to each so it seems like it is coming from the exact right spot.
I just mean that there's no real reason you'd want your xbox to know your speaker placement and do any of that processing. If you have that kind of setup then you have a receiver which is already configured to know where your speakers are and process everything correctly.