OK, thanks!
I took the word "dry" literally and I was confused. This is a good technique for planting on the hills, avoiding the risk of substrate going down the hill and uprooting the plants.
I am planing the same method for my next project, in the shape of wabi kusa. This mean that the plant will stay without water but on a substrate flooded. The aqvarium will be covered with plastic or a glass cover. In the cover I will have a small hole for a small pipe from which I will add CO2 and water, as much as is needed. I have already made such experiment and it works perfect (
https://www.ukaps.org/forum/threads/my-first-wabi-kusa.50033/).
Maybe you should try too, it will rush it for sure.