The idea is that the plant will focus attention on growing roots vs. leaves, not sure if there's any science to it, sounds right, but never bothered to look into it. I've done it both ways and really haven't been able to see any difference one way or another. The huge difference to me was switching to an aero cloner, 90% + success rate every time, DIY cost ~$60 including the pump, will never go back unless it's convenient or don't have the room/cabinet available to clone. Funny thing is I'd have all kinds of issues with gels, rooters and all the crap they sell to make it "easier/better". A few weeks ago I didn't have the room to run the cloner, so I cut 4 clones from a flowering plant at about 3 weeks, stuck them straight into a cool soil mix and my veg cabinet, 3 of them rooted within 10 days, go figure...