macOS really wants to do different things for TVs vs monitors, so if it decides your monitor is a TV for whatever reason, it’ll probably prefer YCbCr and also not offer any HiDPI modes except exactly 2x
2560x1440 is a strong indicator of a monitor, but 4k over HDMI tends to get detected as a TV
That makes some amount of sense, I avoid using HDMI if at all possible. Even on other platforms I’ve generally had less trouble out of DisplayPort and USB-C DP alt mode. I wish it became standard for TVs to have at least a single DisplayPort, it’d make hooking computers up more pleasant.
2560x1440 is a strong indicator of a monitor, but 4k over HDMI tends to get detected as a TV