That also has been an ongoing YT App bug, and most people can get supported playback by either just clearing the app's cache or further modifying a table file inside their config ones (not sure about the specifics, but they're pretty much a Google search away). Yes, the phone won't display a higher resolution than it can, but if you see the 1440p resolution available, that pretty much indicates that the 4K version (2160p) is also in the works/available. But like foxbat stated, you will not see the 2160p resolution unless the device you're using supports said resolution (or you go to a PC and use a browser).