Exactly. Adding the 0.1mm shim only decreases the compression so that the engine becomes a little easier to turn over and get started.
In the beginning the pinch would be at its tightest, so that 0.1mm just makes things a little easier because of the lower compression. Once the pinch lessens, then take out that shim so that it runs the way it should run, unless it just so happens to perform better with that added shim on the track you run at.