musk wrote:CAD programs create infinite resolution models which are only converted to polygons when exported to .stl as a final step. In that case, default export settings usually give a very smooth and poly-heavy result as there's not much point in exporting a low-detail model from cad.

This is not quite the full picture.

As you say, Some CAD programs, notably the traditional ones, use an internal complex geometric/topological representation based on lines, splines, circular arcs. etc. FreeCAD is one such example as it is based on OpenCasCade, there are many other commercial equivalents like this. The discretization to polygons happen on export to STL, where the polygons are always triangular.

However,several other CAD programs, like OpenSCAD, use an internal polyhedron representation where essentially the surface of any solid is described by flat polygons. You can typically request a high discretization and obtain very close approximations to the original smooth geometry. The boolean operations here work on polyhedrons, so the discretization happens at an earlier stage. You will find that some people actually (mis)use the early discretization to get certain effects. an example from OpenSCAD : cylinder(r1=10,r2=0,h=10, $fn=4);

You would think this would generate a cylinder, but what you really get is the great pyramid of Giza