The reason for doing it this way instead of using sketchup s built in section cut tool is that this way eliminates the empty spaces where a mass has been cut revealing the geometry below.
Floor plan section cut.
The direction of the plane through which the section is cut is often represented on plan drawings and elevations by a line of long and short dashes called a section plane.
Plan drawings are in fact a type of section but they cut through the building on a horizontal rather than vertical plane.
This means that you have an imaginary plane cutting through the building at an elevation of 4 feet above the floor.
It is also called a plan which is a measured plane typically projected at the floor height of 4 ft 1 2 m as opposed to an elevation which is a measured plane projected from the side of a building along its height or a section or cross section where a building is cut along an axis to reveal the interior structure.
Therefor you see in the cut anything that the plane passes through.
A floor plan is the most fundamental architectural diagram a view from above showing the arrangement of spaces in building in the same way as a map but showing the arrangement at a particular level of a building technically it is a horizontal section cut through a building conventionally at four feet one metre and twenty centimetres above floor level showing walls windows.
It displays a list of section views and floor plan views.
If part of a floor is cut through the floor should appear to be solid instead of showing any lines from the top of the walls on the floor below.