That's actually not true. I installed the Wii version of the Mii channel on the vWii because wuphax wouldn't restore my backup for some reason, and it was stuck booting into the payload screen. And doing it through nusdownloader restored it.I copied my Wii Miis to the vWii Mii Channel just fine using Wii Save Manager same way I copied my save data, just NEVER attempt to replace the Mii channel on vWii with the one from Wii, you’ll definitely brick your WiiU.
Also, doing things from the vWii will not harm the Wii U in any way. They're technically two separate systems.