it makes no sense to cycle the "empty" water
Well it does work. There are enough bacteria hanging round in the empty tank, on new substrate, on the surfaces even on a brand new tank, even just falling from the air and from you as you set up your tank, place your hands in the water and drip sweat as you carefully arrange you scape. My mates tank I helped him set up was done like this. He got ammonia spike, followed by nitrite spike and finally increasing nitrate. Took maybe 8 weeks, in which he did nothing....except wipe some green algae off glass and move a few plants around. Light was only running 3-4hours a day, when he had the plants in.
Also my initial tank was set up using dried dirty media. The previous owner of my tank had emptied it out for pickup, but carefully dried the filter sponges in his airing cupboard. Anyway placed them back in filter, filled tank with substrate, a few plants, water and fish (also given away with the tank). Sat there with my brand new ammonia test kit and Amquel (removes ammonia) and ready water changes, but nothing. Zilch on ammonia test kit. Even had to go and buy some ammonia from Homebase to prove test kit was working, which it was. So dried filter media survived.
As I had so much ammonia left over, I found other used. Great use is cleaning mucky shelves from your oven. Put the shelves in a poly bag (outside
), douse with ammonia, leave outside to a day or two (it stinks) and you will find the grease/gunk just wipes off the shelves leaving them sparkling like new.