99% of the audio from an Xbox is compressed. All gaming audio as well as streamed video audio. The Xbox might send it out as LPCM multichannel audio but it is just converting the previously compressed stream.

The 4k120 / HDR video will have a lot more impact from the Series X than HDMI audio, unless you're talking volumetric surround (Atmos, etc.).

558.2 amp, Meridian A500 speakers, M2500 sub, Director & Explorer DACs