Quick, dumb question: the interface renders at 1080p, but the console's scaler output is still pegged at your optimal setting, I assume?
If the HUD is just not rendered in UHD detail then so be it (for me, at least,) it's just a waypoint/shop/chooser or what have you. If the signal ever had to change, however, that'd be a real drag on all that speed since I've yet to use a TV that switches resolution/framerate anywhere close to seamlessly. (I don't have an Xbox One X so I don't know what the experience with the hub is like there.)