You are right, not that your friend is necessarily wrong. I usually water right before lights on, halfway into the lights and then an hour before lights out. I do not water after lights out unless my plants call for it. Watering after lights out just raises the humidity in the garden. Then again, I have had plants that asked to be watered 4 times daily and the timer that I had was a 30 minute timer. I am now a bit more religious having a 15 minute interval timer for water my 2'X4' American Hydroponics Bigfoot table. The drain allows the water to get 3 -3 1/2inches deep as it comes up near the tops of my 4'X4" rockwool cube. I line the table with coco mat to keep the roots from becoming exposed and dried out when they jump out the bottoms of the cubes. They just grow right into and/or through the mat to keep them from being exposed to light.
If it ain't broke, don't fix it!!!!!Best of luck! Take care and be well....