Good question. There are several benefits and the main reasons are that it helps to remove white lime and salt deposits that can accumulate on the surface of the soil over the year which affects the pH and nutrient availability. Secondly it provides some fresh nutrients and organic matter for the plant’s root system.
The app and soil/potting instructions are very good imo. It's good to see these kind of details included in it's caresheets. Just replace top layer with whatever substrate is recommended on the plants profile.
A few other positives of changing the top layer are that it improves the soil’s aeration and water retention by loosening the compacted or sunken soil. It can also reduce pest infestations, especially those that like to stay in the substrate, such as fungus gnats and springtails.
