Hello Mauricio,
Uncharted 4 supports YUV420 for some reason and dosent play at 2160 RGB,i have bought a new tv since and this tv is 4k HDR as even on this tv it plays on YUV420 even though i set the ps4 pro settings on 2160 RGB it still only plays using YUV420.As for the 4k on the game your on about it dosent give a option in game menu to change resulution so i cant switch between 1080p and the 1440p the game is set on ps4 pro,it upscales the 1440p to a 4k resulution,on my new tv it looks great as i also get to use HDR but on the samsung ju6000 i also remember it looking good as well