Well the sugar leaves on the plant are pretty valued, Im going to be keeping mine for kief and hash. But I dont see why you couldnt do it if you plan on harvesting soon, and dont want the sugar leaves.
I grow and I dont stress much. People get a little too caught up in the sciences of the plant, Ive seen pretty successful harvests grown with nothing but miracle grow nutrients and tap water. Some cheap bug spray, and thats about it. Unless this dude has like a HUGE garden, I could see that.