The latest beta for Xbox Series X|S has been configured to recognize and better support 3840×2160 UHD televisions. Lower prices for 4K UHD televisions are motivating more to upgrade their televisions for brighter color and clarity. 4K televisions are now pretty much SWAG now.
Lets face, 4K televisions are now so low cost that HDTV is now hardly even stocked anymore. Every year 4K televisions are cheaper and cheaper.
At present the Xbox system software is not very viable at 4K which is why work on the UI is being done to solve the problem once for all.
Once testing is done the new UI may be fine tuned before it is finally released.
Xbox has its work cut out. This fall more new 8K televisions will be entering the high end of the market. Now that HDMI 2.1 has more bandwidth it makes the case for movies and games to be played at even higher resolutions.
For now 4K will be SWAG for at least a few years as 8K is still a rich boys toy.