I've heard of it but I am yet to see anyone with consistent results. For that matter, I am yet to see anyone prove any definitive positive results with this method. I don't believe this would help induce flowering any quicker, personally when I switch to 12/12 I just do it. I don't do it gradually, or any extended periods of darkness. One day I run 24 hours of light, the next I run 12 hours of light 12 hours of dark.
The thing about this, or any experiment for that matter, you have to do so many normal grows to be able to have a consistent number. Then, you have to be able to have a control grow going simultaneously and identical to the grow that you want to experiment with. If you do not have a control group there is no way to be sure the change came from your new variable, and not something else. Then, if you believe that you have found a change, it needs to be verifiable over at least several more grows, and other people should be able to duplicate the experiment and get the same results.
I understand that it would be beneficial to to induce flowering in a shorter period of time, but I would be worried about unnecessary stress to the plant. When people plunge a plant into darkness for the last two days before harvest, I don't believe it does any good, but I also believe it does very little harm. IMO, two days in dark are two days that you are robbing a plant of photosynthesis and if anything would have an aversive result. The difference between doing that at the end of the grow and when you want to switch to 12/12 is that you still have your entire flowering cycle ahead of you and extra stress could have bad results with enough time to show themselves.
I have nothing against experimenting, I believe that is how we get progression. I do believe though, experimenting should be left to those with ample room that can afford to trash an entire grow if they do something that may cause a hermie. For people like myself, who have one small grow going at a time, experimenting must be kept very conservative because loosing a couple months worth of plants would be a very hard to swallow setback. I may experiment with the amount of nutes I use, but I have learned the hard way not to experiment with light cycles. The light a plant requires to veg or flower has been ingrained into it for many, many generations and is pretty cut and dry and shouldn't really be tampered with. Most ofd this is just my opinion, and I'm not trying to discourage anyone from maybe discovering something new and exciting, I'm just saying for the small closet grower, be careful.