Windows generates that from whatever, its not like I directly tell it what to put there.
Interestingly if you go to the "Advanced" tab in that dialog, where you can pick the shared format, it'll happily list 24-bit there, so it clearly knows that 24-bit is supported, so no idea what Windows is doing.
And yes, its limited to 192 kHz, mostly because the Windows mixer really gets unhappy at higher rates, and to 8 channel, because anything above that has no common channel layouts and once again confuses Windows.