in my experience with my current grow i would have to agree with this . I have 9 plants all started in 3 groups of three aprox a week apart in 6" pots . the first group got 4 to 5 weeks veg and the roots had filled the 6" pots they were started in ,the second group the roots were well spread and the third the roots and soil was pretty loose when transplanted . meaning the third group only got 2 solid weeks veg and the root still developing. I put them all on 12/12 two weeks ago and the first 6 have nice bud development and large root mass in the pots . The three with the least veg time i know are still developing root mass and are just starting to show buds and i believe another week would have been beneficial to these plants development before inducing flowering .
I will mention that the first 3 were bag seeds and planted them first for sexing the next are feminized 2 skunk specials , 1 sour nl x haze and the last 3 fem grapefruit which i have grown before highly successfully with only 2 weeks veg time After that shit yes proper development in veg cycle is very important quality , yield and length in flowering .