4k120 is interesting because gaming consoles have it, but an extremely expensive GPU from a few years ago like 2080Ti doesn't (with HDMI you need HDMI 2.1).
Well, consoles "have" it, in the same way that last gen consoles "have" 4k60 or PS3/360 had 1080p60. They have a video interface capable of transmitting such a signal, but not hardware capable of producing that in basically all titles. Also the 2080 Ti had a 4k120 output over DisplayPort 1.4a .
