XB1 is also able to stream SuperHD but only for certain people it seems.
If you load up a video called:
Example Short 297.36 ( Not sure on the numbers. I can look it up if need be. )
It will display the bitrate of the video. 5800 is their "SuperHD" bitrate. Some people who have an XB1 have been able to hit that number. I can't. The highest I've gotten is like 3750 but it always bounces back out of that range.
My Smart TV is able to consistently reach and stay at 5800 and my ps3 in my bedroom is able to hit 3750 and stay there (My bedroom TV is only 720 so it can't get any higher).
I'm not sure why this is the case. My xbox is wired and my download speeds test at 60/10.
your provider could be throttling certain services.