X1 4K Autotuning

This has been an ongoing issue where the XG1v4 4K DVR does not autotune to the 4K version when selecting the HD channel.   Looks like we finally know why.   Xfinity recently added an actual channel for 4K golf (ch 1353 GOLF4K) and the first round of the Players Championship is on now.  Beautiful in 4K HDR! 

If you tune to the regular HD golf channel, the X1 autotunes to the 4K channel, just like it's supposed to.  What's different?  GOLF4K is an actual linear channel rather than an ip connection like all of the other 4K sports events except for the Olympics.  Now we know.