I recently bought a 240 Hz OLED monitor as well, but to my dismay the 80 Gbps data rate mode is actually optional in DisplayPort 2.1a. Even though I have a DP2.1-capable GPU (9070 XT) and monitor, it's not possible to do 4k 10bit HDR at 240 Hz with DSC off. Since I don't want compression to be on I've compromised to sticking with 180 Hz, which as you say due to the diminishing returns above 120 is still plenty.
Still quite frustrating that the display industry did it again in specifying a standard that makes most of what's interesting about it optional, so everyone can print it on their boxes without delivering the expected value.
Psychology more than anything, to be honest. I know it's supposed to be visually lossless, but it does touch and nudge many pixels, and I just want the raw image. I do dabble in graphics and UI frontend at times, and I don't want to take chances. It's something that spending a little more time digging into the algorithmic details of DSC might address for me, but I haven't so far.
DSC has Rate Control, so the very minimal compression needed to go from from 180 Hz to 240 Hz will be negligible except in artificial scenarios like random noise. DSC is intended to be visually lossless up to 3x compression levels.
Still quite frustrating that the display industry did it again in specifying a standard that makes most of what's interesting about it optional, so everyone can print it on their boxes without delivering the expected value.