that's the craziest thing i've ever heard. deprive them of light which would make them stretch in order to keep them from stretching?Turn your grow lights off for three days before going 12/12 and your plants won't stretch
i'll give that a shot with one of mine that i know pretty well; one thing to note with sativas is alot of that stretched out part will often fill with bud...3 days is "crazy", but twenty four really helps sativas to set buds without crazy stretching, in my personal experience. First read about it in high times, Arjans suggestion.