Because, apparently he plans to grow outdoors, and if you only had an initial 12 hr dark period the plant would be confused the very next day outside. Not enough time to fully tansition to flowering. But a week, you're right, much too long.

So, xtcistheshit, outside right? How long of a flower period are you thinking of? It seems to me that the whole point of harvesting sept - oct is because of the length of day that time of year. It is natural for them to become due then. I am not even sure you can get a good healthy flower cycle in this way. But, I am just a grind it out inside kinda guy.