Probably not wise to mix directions, use one set of directions or the other. The [My Cloud Gen2] Using an 8TB HDD and Formatting Failure (Error Code: 600) directions do not indicate creating any directories. Looks like that person just copied the extracted usbrecovery.tar.gz boot folder and the four files within it to the SDX3 (EXT4) data partition.
This will likely be one of those times where one will have to try it and see if it works. If it doesn’t, try a different method or set of directions.
