It probably depends on how you define a cycle "done correctly".
If you are cycling using pure ammonia, and dosing X amount per day constantly, I can see where you might be simulating a 50% bioload and building up the bacteria to deal with it. Once your system can eliminate that much ammonia quickly, then you could stop dosing the ammonia and quickly add a whole bunch of fish. In theory. Perhaps that's what "done correctly" means to the person that wrote that advice.
But I wouldn't follow it. For me... too much room for error. Plus, you want to be quarantining all fish coming into the tank and quarantining a bunch of fish all at once is a daunting task in itself.
Better to just cycle the tank "normally", then add a fish or two per month. Way better chance of success going slowly.