Too many cells of the octomap cleared in moveit

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I am trying to understand how the octomap is cleared around a collision object that is added to the planning scene in moveit. I thought I read somewhere in the documentation (although now I can't find where anymore) that only the cells adjacent to the collision objects are cleared in the octomap, but my experiment seems to lead me to think otherwise.

Please see the image above. In the image, you can see the octomap before and after an object is added to the scene. As you can see, many cells around the object are cleared, not only the adjacent ones. Is there a parameter of moveit that allows to change this behaviour and to clear only the adjacent cells ? Thank you !