I know a bit about Class A from read in wiki and somewhere, but I don't know about automotive industry, why its require class A surfacing? and for what? If only for viewing if surfaces already in high quality class A or not or in short for visualization in PC why not using general 3D app like Maya or Max? Is class A surfacing is needed later in true real production?
because if its only usable in Pc, I'm not see any different from visual/render between class A and general 3D surface
Class A surfaces are normally used for visible surfaces, The reason is the representation due to optical refraction and light reflexion. This surfaces look "pretty"
As an opposite imagine a dent at your car ;)
From my knowledge Manufacturing purpose.
In blueprints notes in finish section:
Surface A: Critical exposed: surface must be smooth, with no scratches, debris, chips or cracks, no gate marks. A good mechanical designer will add: Color/finis to match approved sample.
Surface B: Partially exposed: edges and surfaces must be clean and free of dents or visible marks.
Surface C: Functional unexposed: Surface features must not alter geometry, function or construction.
This notes are very important for vendor or production area and have a huge impact in finish/final part price. Later will be used by quality control and avoid a lot of unnecessary rejections. For quality control designer can add specs like no scratches/ marks bigger then 0.5mm, color specs or other information.
I m not sure why you will need this surfaces in rendering