Beta Insiders will get Dolby Vision for Gaming

The last insider update was focused on the dolby vision, and since it's a beta version, bugs can occur, I believe it's a bug of the build itself, others might be experiencing as well, but I do not get any other reports of this yet. But since you have reported it on the insider hub, others will too, i believe, and this will be addressed by the Insider development team.

Yes, Xbox One X does support Dolby Vision with games that have the feature. Mind that this is 12bit color and not simply 10 bit color.

The feature may be only with select insider rings in the xbox insiders program for now, it may not be out to the general public yet. You can check below to see if it's available on your console:

To setup this feature, first check if you have a compatible TV by going on your Xbox to the 4K TV Details page under Settings. Look for "Your TV supports Dolby Vision" there.

Next, enable Dolby Vision on your console by navigating to Settings -> Display and sound -> Video output -> Video modes -> Allow Dolby Vision.
Read more at
https://news.xbox.com/en-us/2018/08/30/dolby-vision-for-xbox-one-1810-system-update/

Of course the Blu-Ray disks I'm using are UHD and have Dolby Vision.

Dolby Vision is enabled on Xbox One X settings, TV HDMI ports are in Enhanced mode (4:4:4 4K/UHD HDR 60Hz), and the TV test (that can be found inside Xbox menu) returns all green ticks for my Xbox-to-TV connection.

As said, Dolby Vision works with all streaming apps... but not when playing Blu-Ray UHD Dolby Vision disks.

Unless your going to fork over 1000s of dollars to get 1 of the 5 manufacturers that have 2.1. Dolby vision will not work with ALLM.

Performance of hdr10 is not relevant nor is ALLM.

Dolby vision does not work with ALLM. This is confirmed that this is by design. You choose between the higher fidelity of Dolby vision over Game mode ALLM.

Hi.

When you start Netflix, does it start up in HDR or Dolby Vision as it seems the app itself launches in that mode. Not all content is Dolby Vision compatible in Netflix.

Your TV is on the list of supported models, and I assume you are in the Insider program for testing this feature?

Also, check for any updates to the Netflix app.