yeah, the "back to NAND" is in fact just a console reset command. on Wii, it looks like you are back to realNAND, but on vWii the reboot just return to wiiu.
You need that channel only on Wii, because on vWii nintendo already has such channel (the one called "return to wiiu").
"Neek" (developed by Crediar) is the term to define this NAND redirection method, by rebooting the entire console into a redirected mode. All the NAND is redirected and the console has zero access to real NAND, unlike the "cIOS nand redirection" used by USBLoaders and mightyChannel where everything is still done on NAND and cIOS is responsible for redirecting NAND access requested by the game in real time. Only specific NAND access command are intercepted by cIOS, that's why some games are not compatible and need full neek mode instead where the kernel is responsible for redirecting everything instead of just game file's access.
Neek can redirect NAND to either SD (S neek) or USB (U neek) (see the pattern ?
)
Neek has an option to also redirect Disc interface (di) to SD or USB, noted by "+di" to load a decrypted file system format game stored on the redirected device.
Neek v2.0 (Neek2o) is a modded version of Neek (not from Crediar), adding more support like subfolder, wbfs, arguments, return to. (for the 4 main features)
S/U/neek/2o : Redirect NAND to SD or USB
S/U/neek/2o + di : Redirect NAND to SD or USB, redirect Disc access to same device.
S/U/neek/2o + di + ext access : usually, ALL the external device is locked and seen as "internal NAND" by the console. IF you want to also use the SD/USB to be accessed by homebrew, there's an option to do it, but it's unstable and dangerous for your data (plus, rarely working).
Did you read my guide?
https://gbatemp.net/posts/6592730
If you had question, and think that this explanation could benefit more users, I can copy it in the guide