They do a similar process in mulit axis machining centers. The plastic stock would be on an arbor (chuck), spining, and while spining, with the waterjet running the plastic is moved into and out of the waterjet, while rotating (yaw) to move the cut from the outside to the middle of the lens element. (boy, do I suck at trying to explain this.)
imagine a wood dowel in an electric drill, with some sandpaper glued to the wall. walk up to the wall with the drill running, push the end of the dowell into the sandpapered wall, and just twist the drill from side to side to "wipe" the end of the dowell against the wall resulting in a rounded end.
Now imagine doing the same thing against a single knife edge, you can still get a rounded,,, or asymetrical end on the dowel just by moving the drill around by twisting it, and moving it in and out. Now change the knife edge to a water jet, just using it as an abrasive surface to work against.
I just have to believe they have multi axis water jet units with live work holders.
Yes , there is a higher end , glass shapers ,ceramic doped magnetic liquid rotate and lens shaped with it.
This is a RIT research , answering the need of stadium big lasers lens making problem.
I dont know they move the lens or they move the waterjet at cnc shop but I think my way - as sinatra sings - not requires 5 , 6 axis expensive machines. They will cut 2D shapes and lap and I will use in the group ready sold aspheric or spheric lens.Only I need a Indian or Chinese designer.
QC , Yes , block must me casted and it will be done with cold casting . It is widely available. I worked in mold making business and smallest mold costs 2500 dollar and it doesnt stop there , you must find special steels , correct modeller , programmer , new cnc machines without lost its calibration , lots of plastic pellets , an powerful injection machine where its owner agree to manufacture your part. And optical plastic coming of injection mold requires flame polishing as steel mold requires also.
Not a amateur way. And extreme temperature control.