The Microsoft decoder does not support TrueHD+Atmos, the most common type, as its found on Blu-ray disc. E-AC3 (also known as Dolby Digital Plus) + Atmos is relatively rare, only used by a few streaming services - which don't let you play through MC anyway. Technically it can also be on Blu-ray, but thats rather uncommon, and personally I would feel cheated to get a lossy audio and then Atmos, rather get lossless audio with Atmos on something like a Blu-ray.
Furthermore, Media Center is not a "Universal" application. That Dolby sample uses some black-box media control, you wouldn't like if we used something like that, as its the end of the MC flexibility.
Additional, as pointed out in the very first post in this thread, Media Center uses DirectShow, these codecs linked above are for MediaFoundation (and its really not quite clear how you would even get them to do anything with the Atmos data)
As far as I could determine, these codecs also support Atmos only in two modes: Bitstream HDMI mode, or Atmos for Headphones. I have yet to see a decoder that could just output a bunch of PCM over the standard 5.1/7.1 channel.
A full Atmos-capable output setup on a PC with 12 or 16 channel, without a Atmos-capable receiver, is just not a design goal for Dolby or Microsoft - which is understandable, since thats a lot of extra work for mixing and output, and no ordinary consumer has such a setup.
Its also important to know that "Atmos" is not one single thing. Dolby uses that name for an entire family of audio technology. A Game that wants to render 3D audio? Atmos. Spatial audio on a Blu-ray? Atmos. Audio in Cinemas? Atmos. All very different technologies.