CNC machines can get ultra precise results. It depends on the speed of your spindle. 18000 revolution is enough to shape any desired strange curves on to lens. They use these lenses at military to laser fusion experiments and there is no way to carve a lens to these shapes with hand.
I am researching reports from databases for least 12 years and I found a vast use of cnc machines to carving lenses.
And I researched impeller making in this time range and all your success and final finish depends on your software , not machine. There are lots of new cnc machines everywhere but few softwares to direct the spindle with correct curves. And these softwares are expensive like a new machine . You must buy the impeller specific software. I am still receiving reports , etc.
Same thing for submarine propellers , 25 years ago Toshiba sold cnc cam software to ABB and they sold it to Soviets , with that software , Soviets accomplished to make propellers 5 times more silence than the past. us banned the toshiba for 10 years.
Other thing for lens cnc is the metallurgy of cutting tools and Leica kept it as secret.