it is true, if no one is feeding that plant and supplying it with a better than average environment. yes, a plant will grow during stretch, whether the pot is already full of roots or not. but it won't grow as many bud sites, and the buds won't grow as large...that is my personal observation, so i can't send you anywhere to confirm it. i've just noticed that the better yielders are the ones that get up potted less than ten days before they get flipped to flower...noticed it enough that it's become my standard practice. i don't care how long the branches get, i care how heavily loaded down they are, and the ones that get repotted later are the ones carrying the most