You read wrong unfortunately. I have an Xbox One S and it does not yet support advanced audio codecs, not even True HD or DTS Master formats and it is a recent purchase with the latest firmware update installed. I had to realize this unfortunately after I had purchased it, but supposedly (sarcastically holding breath) there's a firmware update coming out this year that will allow the Xbox to properly make use of those formats. Microsoft fell way short on this one, IMO, doing very well by incorporating 4k blu-ray capability into the machine, but simultaneously shooting themselves in the foot by not considering the proper audio codecs. Atmos, DTS: X.. fugghedaboutit... at least for now.
So here's what you get in the meantime:
Assuming you're using the HDMI output from the Xbox, it will allow you to select either stereo (2 channel) audio output, or either 5.1 or 7.1 uncompressed multi-channel output via PCM. It will give you the option to select bitstream output as well, but then it ties you to either encoding that signal as standard Dolby Digital or standard DTS and none of the advanced formats. I find this particularly annoying. Usually a bitstream output will let the receiver decode the signal and play it in its native format/codec. But these bitstream options will limit you to standard DD or DTS only. If you choose you can also hook up an optic cable and output your audio via optic which is also selectable in the Xbox audio settings, but the same limitations apply here and you're not going to get anything higher than standard DD or DTS.
I have mine currently selected to Uncompressed 5.1 out which seemed to be about the best option available from the console until that firmware update appears. My AVR sees it as multi-channel in and will basically pass that signal along to the appropriate channel outputs. It sounds good, but I lack (and miss) the ability to see that nice indication that Dolby Digital True HD, DTS Master, Atmos, etc. are actually being used.
That being said, it does a pretty great job of displaying 4k content on my Samsung TV via the AVR. I used to use an old PS3 for my blu-ray player so naturally got the Xbox when upgrading to 4k - one other minor thing to note here: While the Sony machine automatically played BD discs without having to install a separate app, the Xbox does not. You have to actually install the app from its online store (it's free), then the Blu-Ray player shows up in your apps list; from there you can play your 4k and standard Blu-Ray discs when you put them in.