Yeah, just another thing that popped into my mind... say we change our Wii U serial number and by some fluky chance, change it to one that already exists (i.e. say if we changed it to the one he used in the video: 454545454, and RiruGreen happened to play online with this serial today)... that would probably raise a red flag for Ninty having the same serial playing Splatoon online. Chances are super slim we actually edit a serial in HxD that already exists, but yeah, this would probably be a concern.I dont think so , that could be because if Ninty sees your old NNID with a different Serial Number , its obvious something bad is going there.
And yes , you have to forcedly launch redNAND or your sysNAND with sig patches (pretending this unbanning method could work on sysnand with sigpatches)
I bet some inexperienced users for example might actually just follow exactly what RiruGreen did and use 454545454 and thus, use the same serials.