Very popular and common in Germany.
you have a completly flat background (insulation / board) and then apply the first layer of basecoat before mesh using the serated spat means that you have exactly the same thickness of basecoat applied to a flat backing.....
embed the mesh into the serated layer (this then ensures that it is all in the same level), then apply a smoothing coat over the mesh, while it is still wet.
This leaves a completely flat basecoat layer, ready for finish coat
At least - that is what all of the German Technicians who I have spoken to about it state anyway!