lol... guys, this isn't even a hack. See that fastboot oem unlock step? That's the intentional bootloader unlock included as a feature. Then they are reflashing the OS image with a new one that allows root, which is EXACTLY what the bootloader unlock is intended to do. Again, this is no hack, this is just someone doing exactly what the feature was intended for.
Show me a root without doing fastboot oem unlock, then I'll be interested.
Also regarding the unroot method, that doesn't really apply when doing the bootloader unlock. Unlocking the bootloader causes a hardware change indicating the warranty is void. There is no going back from that.
Know what you're getting into.