Just bought the MPG 321CURX QD-OLED. My first MSI purchase in awhile because I figured what the heck, it is not a motherboard or graphics card. How badly could MSI screw up the engineering of a monitor? Answer... Epically! When I saw the 3 foot power cable I immediately stated "Aww adorable". Then there was the moment they made me laugh so hard I almost pee'd myself. They actually show a diagram of you supposing to run this cable thru the management holder in the back of the monitor! Not only is this hilarious and impossible; I believe it violates United States false advertising laws.
Looks like paper manual is outdated. But any person above the age of 15 should be able to try and see whether that works or not, and conclude that the manual may be wrong. And these things happen.
In the online manual it only says what it is for. It does not tell you or even suggest to run power cable through the "cabe routing hole".
And under no circumstances this would fall under false advertisement. You never checked the manual before ordering the monitor, especially as it's a paper manual and online version is corrected ( I suspect this mistake was corrected immediately but didn't make it to already printed / shipped manuals ).
For the monitor I have, 321UP, it shows a similar diagram explaining what each thing is for. And I was able to push the power plug through the "cable routing hole". Bit tough, but it went through.