Those bearing balls you list are all various grades of stainless steel and their hardness has nothing to do with their sphericity grade. Type 304 and 316 stainless steel are "austenitic" stainless steels and cannot be heat treated effectively. Type 440 stainless steel is a "tool steel" stainless and can be heat treated to high hardness so it's greater hardness is due to it's composition, not because it's "rounder".

If you compare standard carbon or "chrome steel" steel bearing balls you will find little hardness differences between roundness grades.