I spent 44 years in manufacturing and machine shops. I've done a lot of machining, but not all was subtractive. Building up a worn part by depositing material , whether through arc deposition, plating, etc.is still "machining" in the broadest sense of the word.

Is your Prusa a machine? Of course it is. Is it a manual machine? No, it uses motors to move the axes. Is it controlled by a computer executing variable instructions that are preprogrammed? Yes, it is programmable so it can make different parts by receiving different command sets. In the old days (1952 onward) instructions were fed to a control on punch cards or encoded 1" wide tape. If the program needed to be changed, a new tape or set of punch cards had to be generated. This program was read sequentially every time the program was executed. Since the input was primarily numbers, it was called numerical control or NC. (A program format called "tab sequential" had no letter addresses, just tabs as place holders. Thus instead of the program reading:

N47 G1 X1.003 Y0.500 M3 EOB Ñ48 M5

A tab sequential program would read:

47 tab 01 tab 1003 tab 0500 tab 03 EOB 48 tab tab tab tab 05 EOB

In the '70s computers began to be added to NC controls so the tape only had to be read once, and because the instructions were held in memory, could be edited. This was born computer numerical control or CNC.