The good news is that you can, but the bad news is that it isn't as described in the earlier posting.
Open your layout in Surveyor,then move to an area where boards are to be removed. Select Topology from the rhs of the screen and select Advanced. Select the Delete button and point the cursor onto the ground that is to be removed. By clicking the left mouse button you will cause a message to appear, "Deleting a section cannot be undone. Delete?" If you select the tick the baseboard you pointed at will be removed.
Two further tips :-
If you delete the wrong area, exit the layout without saving.
Even if you are selecting the right boards to delete it is prudent to Save the layout after every few boards have been deleted.