Basically, it won't turn on normally anymore. With AutoRCM installed, the console screen is not going to change when you press the power button. This is indicative of the console entering RCM. The sole purpose of RCM is to hook it up via USB connection to a device that is capable of sending payloads in order to load hacks. What this guide does is provide a foolproof way of booting RCM.
See, normally when you update your system, your console reboots itself. The reason it reboots itself is because during the initial startup of the console, it checks the number of fuses burnt with the current firmware. After a system update, your firmware is higher than the number of fuses burnt so it burns fuses to compensate. See the bottom of this for the full breakdown:
http://switchbrew.org/index.php?title=Fuses
AutoRCM ensures the console will never do this by forcing the user to turn on the console using hacks.