Congratulations on your new Camaro
No need to kill the engine and wait for it to cool down at all, just vary your speed, don't drive at a constant 65-70-75 mph in the same gear for hours. Enjoy a few little half throttle, 3.5-4k rpm bursts from 30 to 70 mph in the right lane, shift down and back up periodically etc.
The idea is that you don't want the engine running at the same rpm under the same low load for extended periods during the break-in. That said, the LT4 isn't made of candy, don't worry, you won't break it with your driving.
Now as to whether or not this is a proper break-in procedure, that is a whole deep rabbit hole that I don't want to descend into. At the end of the day, this is the official recommendation from the manufacturer, and you will find plenty of information even here on this board if you're interested in more details.