Good to know! Seems that it does behave a bit weird if DSC is in use. I had no problem with this when using the CRG9 but since that tops out at 120 Hz without DSC I guess that's why it worked.The problem is that prior G9 models 3440x1440 @ 240hz doesn't even work (it isn't even a option in the EDID). These DSC monitors aren't really happy with custom resolutions. You can read on reddit all the work arounds people have had to use or try but it ends up breaking HDR or VRR.
I'm hoping Samsung just includes some of those resolutions out of the box.
Samsung does these incremental improvements then never ports them to their older models. As an example, the CRG9's preset functionality was pretty much garbage - you could not assign most of the OSD options to the presets. Then the Neo G9 (ugh, why could they not call the new one Neo G10 or Neo G9 8K or something?) fixes that where most settings can be stored in the preset. Then weirdly they seem to have removed this functionality completely from the Neo G8. I hope they don't do that for the new Neo G9 as those presets are useful.