In case anyone ever runs into this in the future, I managed to discover that the issue is with DSC specifically. Disabling it gets rid of the issue entirely, however then you can't run 240hz+HDR/10bit colour.
After doing some research over the weekend I found that I wasn't the only one experiencing these issues. I found a handful of reviews on Amazon describing similar artifacts to the one I had (even though the Dell technician I talked to claimed that they have never heard of such issues before). Additionally a user review on the website of the store I got it from popped up with the user describing going through 5 of these monitors, all of them with major defects (dead pixels, large patches of dust under the screen), before settling on one with the least amount of issues.
Overall I would not recommend this monitor despite the glowing reviews it receives unless you're willing to gamble with the QC and to potentially go through several returns.