Yeah I just tried to delete all content and it requires an internet connection :/ I'll probably just delete the previous owner's accounts and data then
When I selected delete everything to system restore the system it attempted to connect to the internet and told me no connection was found, I didn't see an option to system restore without connecting to the internet in general
n the 3DS it just needs a internet connection to unlink the NNID, but it doesn't force update, there was a bit of paranoia about the sudden "internet required" part, but it was fine and its only required to unlink the NNID.....i presume its the same with the wiiu
I did have a used Wii U console at one point, and formatted it (no NNID on it) ...It also prompted me to connect to the internet?? No idea why??
I'm pretty sure I just unplugged my router from the internet, and then allowed the used Wii U console to connect to my router and it formatted fine.