..wish that objects only cut their own exact shape in the ground, and not a rectangular hole...

If I understand your point, it is possible to achieve this, but you will have to add a cutout your model, using the FurnitureLibraryEditor and adding SVG. It is, by the way, sometimes faster to go straight for Home.xml and add the cutout there.

Either way, you need to be able to describe the cutout in an SVG path, and true, it is not for the faint hearted first time user, but then, your design is pretty advanced too... [:)]

And if you wish for a SVG cutout for a special model, just ask.

ok

PS. In some thread about the release of a new version, there are comments on why windows have automatic cutouts, while stairs do not.