I believe a Rest Day is to allow your plants to use extra nutrients in the water column. You are not "wasting" as many nutrients as you are when dosing straight through. It also keeps everything nice and orderly which will help you to pinpoint any problems that may arise along the way. Humans like order. We also like holidays. A Rest Day will give your arms, measuring spoons, fish, and plants a holiday. Perhaps there is some logic to that feeble explanation? I suggest that you do what you want to do with your dosing as long as it is working for you. If it is not broken, don't fix it.