Perhaps it has to do with the older HDMI version that may not support 4K on all Hoppers vs. the HDMI 2.0 presumably on the 4K Joey. Just a guess, but that is the ONLY reason I can think of that would make it impossible for the Hoppers to display 4K content, and the Hoppers (both versions) were designed a fairly long time ago (design 1-2 years PRIOR to mass manufacture and release to the public) when 4K just barely appeared to being a real thing. Heck, at the time DirecTV and Dish were putting together the Hopper and Genie, MOCA 2.0 came on the scene too late to be included even though it was finalized BEFORE manufacture of those boxes, but probably AFTER the design for the Hopper and Genie were finalized. The time it takes to get a device all done and commit to the vendors for parts, etc., and then to manufacture in large numbers and get it out means that technology can significantly improve and move along long before the first such device is available for purchase of installation.