This might be right if the option to configure wasn't disabled for the Realtek Optical Output. Clicking on Properties instead, and going to the Supported Formats tab, I can select and test both Dolby and DTS. Both work.
My suspicion is that Dolby, DTS and MS worked out some kind of deal to try and prod people into using Atmos and DTS:X Ultra
Read carefully, it tests whether your av receiver can do Dolby or DTS. It doesn't test whether your computer can do Dolby or DTS.
There is no deal and that's the problem.
Google/Youtube and Microsoft are trillion dollar companies and they decided to not pay tiny Dolby any money. Google went as far as creating their own video and audio codecs so that youtube doesn't have to pay anyone any money.