I have the Sony X800d 43 inch as well and agree HDR looks fantastic although I am not using rtings recommended settings.
As with all HDR sets you just need to fool around with your TV's picture settings until you get it perfect. It took me awhile but I am really happy with the results. To my eyes MLB The Show 19 colors really pop and are vivid while still looking very natural and realistic.
And as TheBleedingRed21 said the Sony X800d is no where near an elite TV so with higher end TV's you should be able to see even better HDR results.