Correct, only one.

This specific turn is onto a street that the article describes as "traffic volume here is low, since only residents will use this street." They probably expect the 1-car buffer to be enough for this intersection. You can see in the video that the 1-car buffer is empty most of the time.

For intersections where they expect more turning traffic (where the one car buffer wouldn't be enough), they add turning lanes that can accomodate more than one car. You can see an example of this a few hundred meters northeast when Graafseweg intersects the Van Grobbendocklaan: https://maps.app.goo.gl/ZmURqawr3oeBX5Sq9