Still, it gives me peace of mind to know that no matter what my Wii U won't be bricked.
Accidents happen, if he lets someone else use the Wii U they might delete the title not knowing, for example.
And we don't know what will happen with the next Wii U update, it might end up bricking anyone with CBHC who updates by accident (and people will update by accident, there's no doubt about that)
If they followed the guide they should be running the dns "blockers" so there shouldn't be any accidental updates.
Isn't there someday of backing up the Wii u NAND without having to resort to rednand method? With the 3ds/2ds and Wii/vwii you can dump the NAND as backup in case of bricks.