Yeah, I think the logic is that you should continue to feed heavy veg nutes to aid the growth spurt the plants go through in those first few weeks after flipping. I'm not sure how sound that logic is though, because the blue cheese in my previous grow tripled in size when I flipped, and continued to stretch well past the 3 week mark. Even though I switched to bloom nutes at 2 weeks, and did defol at 3. Next run, I will switch nutes at 2 weeks again.