no one said flushing is required to maintain a healthy plant over time. It is not required pre harvest. Why starve a plant when it need nutes most at this time. Not saying go crazy with them but they still need food. Flushing is kinda like stealing from yourself.
Brick top had a really good post about this topic. With university studies about 72 hrs of darkness. Try and find it. I personally do it. It doesn't cost anything to not run the lights for 3 days. From what I read in his post i was convinced.